ISO 11277:1998
(Main)Soil quality - Determination of particle size distribution in mineral soil material - Method by sieving and sedimentation
Soil quality - Determination of particle size distribution in mineral soil material - Method by sieving and sedimentation
Specifies a basic method of determining particle size distribution applicable to a wide range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with the less common soils mentioned in the introduction. This standard has been developed largely for use in the field of environmental science, and its use in geotechnical investigations is something on which professional advice might be required.
Qualité du sol — Détermination de la répartition granulométrique de la matière minérale des sols — Méthode par tamisage et sédimentation
Kakovost tal – Ugotavljanje porazdelitve velikosti delcev v mineralnem delu tal – Metoda s sejanjem in usedanjem
General Information
Relations
Frequently Asked Questions
ISO 11277:1998 is a standard published by the International Organization for Standardization (ISO). Its full title is "Soil quality - Determination of particle size distribution in mineral soil material - Method by sieving and sedimentation". This standard covers: Specifies a basic method of determining particle size distribution applicable to a wide range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with the less common soils mentioned in the introduction. This standard has been developed largely for use in the field of environmental science, and its use in geotechnical investigations is something on which professional advice might be required.
Specifies a basic method of determining particle size distribution applicable to a wide range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with the less common soils mentioned in the introduction. This standard has been developed largely for use in the field of environmental science, and its use in geotechnical investigations is something on which professional advice might be required.
ISO 11277:1998 is classified under the following ICS (International Classification for Standards) categories: 13.080.20 - Physical properties of soils. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO 11277:1998 has the following relationships with other standards: It is inter standard links to ISO 11277:1998/Cor 1:2002, ISO 11277:2009; is excused to SIST ISO 11277:2006/Cor 1:2006, ISO 11277:1998/Cor 1:2002. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
You can purchase ISO 11277:1998 directly from iTeh Standards. The document is available in PDF format and is delivered instantly after payment. Add the standard to your cart and complete the secure checkout process. iTeh Standards is an authorized distributor of ISO standards.
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11277
First edition
1998-05-15
Soil quality — Determination of particle size
distribution in mineral soil material —
Method by sieving and sedimentation
Qualité du sol — Détermination de la répartition granulométrique de la
matière minérale des sols — Méthode par tamisage et sédimentation
A
Reference number
Contents Page
1 Scope. 1
2 Normative references. 1
3 Terminology and symbols. 2
4 Principle . 2
5 Field sampling . 4
6 Sample preparation. 4
7 Dry sieving . 4
8 Wet sieving and sedimentation. 6
9 Precision . 19
10 Test report. 19
Annex A: Determination of particle size distribution of mineral
soil material that is not dried prior to analysis . 20
Annex B: Determination of particle size distribution of mineral
soils by a hydrometer method following destruction
of organic matter. 23
Annex C: Bibliography. 30
© ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet central@iso.ch
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Printed in Switzerland
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ISO ISO 11277:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work of
preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 11277 was prepared by Technical Committee
ISO/TC 190, Soil quality, Subcommittee SC 5, Physical methods.
Annexes A and B form an integral part of this International Standard.
Annex C is for information only.
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Introduction
The physical and chemical behaviour of soils is controlled in part by the
amounts of mineral particles of different sizes in the soil. The subject of this
International Standard is the quantitative measurement of such amounts
(expressed as a proportion or percentage of the total mass of the mineral
soil), within stated size classes.
The determination of particle size distribution is affected by organic matter,
soluble salts, cementing agents (especially iron compounds), relatively
insoluble substances such as carbonates and sulfates, or combinations of
these. Some soils change their behaviour to such a degree upon drying,
that the particle size distribution of the dried material bears little or no
relation to that of the undried material encountered under natural
conditions. This is particularly true of soils rich in organic matter, those
developed from recent volcanic deposits, some highly weathered tropical
soils, and soils often described as “cohesive” [6]. Other soils, such as the
so-called "sub-plastic" soils of Australia, show little or no tendency to
disperse under normal laboratory treatments, despite field evidence of a
large clay content.
The procedures given in this International Standard recognize these kinds
of differences between soils from different environments, and the
methodology presented is designed to deal with them in a structured
manner. Such differences in soil behaviour can be very important, but
awareness of them depends usually on local knowledge. Given that the
laboratory is commonly distant from the site of the field operation, the
information supplied by field teams becomes crucial to the choice of an
appropriate laboratory procedure. This choice can be made only if the
laboratory is made fully aware of this background information.
All procedures in this International Standard should be carried out by
competent, trained persons, with adequate supervision. Attention is drawn
to certain known hazards, but it is essential that users follow safe working
practices. If in any doubt, seek professional advice.
It is essential that users of this International Standard read all of it
before commencing any operation, as failure to note certain points
will lead to incorrect analysis, and could be dangerous.
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INTERNATIONAL STANDARD ISO ISO 11277:1998(E)
Soil quality — Determination of particle size distribution in mineral
soil material — Method by sieving and sedimentation
1 Scope
This International Standard specifies a basic method of determining particle size distribution applicable to a wide
range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with
the less common soils mentioned in the introduction. This International Standard has been developed largely for
use in the field of environmental science, and its use in geotechnical investigations is something on which
professional advice might be required.
A major objective of this International Standard is the determination of enough size fractions to enable the
construction of a reliable particle size distribution curve.
This International Standard does not apply to the determination of the particle size distribution of the organic
components of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It should also
be realized that the chemical pretreatments and mechanical handling stages in this International Standard could
cause disintegration of weakly cohesive particles that, from field inspection, might be regarded as primary particles,
even though such primary particles could be better described as aggregates. If such disintegration is undesirable,
then this International Standard should not be used for the determination of the particle size distribution of such
weakly cohesive materials.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 565:1990, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings.
ISO 3310-1:1990, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth.
ISO 3310-2:1990, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal
plate.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
ISO 11464:1994, Soil quality — Pretreatment of samples for physico-chemical analyses.
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3 Terminology and symbols
3.1 Terminology
Particles within particular size ranges or classes are commonly described as cobbles, gravel, coarse sand, silt, etc.
The meaning of such trivial names differs between countries, and in some cases there are no exact translations of
such words from one language to another; for example, the Dutch word "zavel" has no equivalent in English. The
only fraction for which there appears to be common agreement is clay, which is defined as material of less than
0,002 mm equivalent spherical diameter [1, 6]. Such trivial names shall not be used in describing the results of
particle size determination according to this International Standard. Phrases such as ".passing a 20 mm aperture
sieve." or ".less then 0,063 mm equivalent spherical diameter." shall be used instead. If trivial names must be
used, for example to cross-reference to another (inter-)national standard, then the trivial name should be defined
explicitly, so as to remove any doubt as to the meaning intended, e.g. silt (0,063 mm to 0,002 mm equivalent
spherical diameter) (clause 4 and, for example, [3]). Further, it is common to use the word 'texture' to describe the
results of particle size distribution measurements, e.g. 'the particle size of this soil is of clay texture'. This is incorrect
as the two concepts are different, and the word 'texture' shall not be used in the test report (clause 10) to describe
the results obtained by use of this International Standard.
It is common to refer to sieves as having a particular mesh-size or mesh number. These are not the same as the
sieve aperture, and the relationship between the various numbers is not immediately obvious. The use of mesh
numbers as a measurement of particle size is difficult to justify, and shall not be used in reporting the results of this
International Standard.
3.2 Symbols
The following symbols are found throughout the text and, where appropriate, units and quantities are as given below
(SI convention is followed for common units e.g. g = gram; m = metre; mm = millimetre; s = second, etc.).
Mg megagram (10 g)
mPa millipascal
t is the settling time, in seconds, of a particle of diameter d ;
p
η is the dynamic viscosity of water at the test temperature (see Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65; note in clause 4);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken as 1,00;
w
note in clause 4);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981);
d is the equivalent spherical diameter of the particle of interest, in millimetres;
p
4 Principle
Particle size distribution is determined by a combination of sieving and sedimentation, starting from air-dried soil [6]
(see note below). A method for undried soil is given in Annex A. Particles not passing a 2 mm aperture sieve are
determined by dry sieving. Particles passing such a sieve, but retained on a 0,063 mm aperture sieve, are
determined by a combination of wet and dry sieving, whilst particles passing the latter sieve are determined by
sedimentation. The pipette method is preferred. A hydrometer method is given in Annex B. A combination of sieving
and sedimentation enables construction of a continuous particle size distribution curve.
The key points in this procedure are summarized as a flow chart in Figure 2. This International Standard requires
that the proportions of fractions separated by sedimentation and sieving be determined from the masses of such
fractions obtained by weighing. Other methods of determining the mass of such fractions rely on such things as the
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interaction of particles with electromagnetic radiation or electrical fields [1]. There are often considerable difficulties
in relating the values obtained by different methods, one to another, for the same sample. It is one of the intentions
of this International Standard that close adherence to its details should help minimize interlaboratory variation in the
determination of the particle size distribution of mineral soils. Therefore the proportions of fractions shall be
determined only by weighing. If this is not the method used, then compliance with this International Standard cannot
be claimed in the test report (clause 10).
Both the pipette and hydrometer methods assume that the settling of particles in the sedimentation cylinder is in
accordance with Stokes' Law [1, 6, 9], and the constraints that this implies, namely:
a) the particles are rigid, smooth spheres;
b) the particles settle in laminar flow i.e. the Reynolds Number is less than about 0,2. This constraint sets an upper
equivalent spherical particle diameter (below) slightly greater than 0,06 mm for Stokesian settling under
gravity [1];
c) the suspension of particles is sufficiently dilute to ensure that no particle interferes with the settling of any other
particle;
d) there is no interaction between particle and fluid;
e) the diameter of the suspension column is large compared to the diameter of the particle, i.e. the fluid is of 'infinite
extent';
f) the particle has reached its terminal velocity;
g) the particles are of the same relative density.
Thus, the diameter of a particle is defined in terms of the diameter of a sphere whose behaviour in suspension
matches that of the particle. This is the concept of . It is the principle upon which the
equivalent spherical diameter
expression of the diameter of particles, as derived from sedimentation, is based in this International Standard.
Stokes' Law can be written, for the purposes of this International Standard, in the form:
t = 18ηh/[(ρ — ρ )gd ]
s w p
where
t is the settling time, in seconds, of a particle of diameter d (below);
p
η is the dynamic viscosity of water at the test temperature (Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65; see note);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken as 1,00;
w
see note);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981);
d is the equivalent spherical diameter of the particle of interest, in millimetres;
p
NOTE — It is realized that there are considerable differences between the densities of soil particles, but for the purposes of
this International Standard it is assumed that the mean particle density is that of quartz, i.e. 2,65 Mg/m [10], as this is the
3 3
commonest mineral in a very wide range of soils. The density of water is 0,9982 Mg/m and 0,9956 Mg/m at 20 °C and 30 °C,
respectively [8]. Given the effect of the addition of a small amount of dispersant (8.3.2), the density of water is taken as
1,0000 Mg/m over the permitted temperature range of this International Standard (8.2.2). Further, for routine use, it is
recommended that the sampling times be converted to minutes and/or hours, as appropriate, to lessen the risk of error
(Table 3).
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5 Field sampling
The mass of sample taken in the field shall be representative of the particle size distribution, especially if the
amount of the larger particles is to be determined reliably. Table 1 gives recommended minimum masses.
6 Sample preparation
Samples shall be prepared in accordance with the methods given in ISO 11464.
NOTE — For many purposes, particle size distribution is determined only for the fraction of the soil passing a 2 mm aperture
sieve. In this case, the test sample (8.5) may be taken either according to the procedures in ISO 11464 or from the material
passing a 2 mm aperture sieve according to 7.2.
7 Dry sieving (material > 2 mm)
7.1 General
The procedure specified in this clause applies to material retained on a 2 mm aperture sieve. Table 2 gives the
maximum mass which shall be retained on sieves of different diameters and apertures. If more than this amount of
material is retained, then it shall be subdivided appropriately, and resieved.
7.2 Apparatus
7.2.1 Test sieves, with apertures which comply with ISO 565, and with well-fitting covers and receivers.
The full range of sieves appropriate to the largest particle(s) present should be used (Table 1; note in 7.2.3). The
apertures chosen shall be stated in the test report (clause 10). The accuracy of the sieves shall be verified monthly
against a set of master sieves kept for this purpose, using an accepted method such as particle reference materials,
microscopy etc. [1] depending on the sieve aperture. Tolerances shall meet the requirements of ISO 3310-1 and
ISO 3310-2. Sieves that do not meet these specifications shall be discarded. A record shall be kept of such testing.
Brass sieves are particularly liable to splitting and distortion, and steel sieves are strongly recommended for the
larger apertures.
Special care shall be taken to ensure that covers and receivers do not leak. Sieves shall be inspected weekly when
in regular use, and on every occasion if used less often. A record shall be kept of such inspections. Round-hole
sieves shall not be used.
7.2.2 Balance, capable of weighing to an accuracy of within ± 0,5 g.
7.2.3 Mechanical sieve shaker
NOTE — It is usually impracticable to sieve mechanically at sieve apertures much greater than 20 mm, unless very heavy-
duty equipment is available. Mechanical sieve shaking is essential to sieve efficiency at smaller apertures.
7.2.4 A sieve brush and a stiff brush.
7.3 Procedure
Weigh the dry test sample, prepared in accordance with ISO 11464, to the nearest 0,5 g (m ). Place the weighed
material on the 20 mm sieve, and by brushing the material gently over the sieve apertures with the stiff brush (to
remove any adhering soil), sieve the material. Take care not to detach any fragments from the primary particles.
Sieve the retained material on the nest of sieves of selected apertures (7.1.1), and record the amount retained on
each sieve to the nearest 0,5 g. Do not overload the sieves (Table 1), but sieve the material in portions if necessary.
Weigh the material passing the 20 mm aperture sieve (m ), or a suitable portion of it (m ) (Table 2) obtained by an
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appropriate subsampling method (clause 6), and place this on a nest of sieves, the lowermost having an aperture of
2 mm. Shake the sieves mechanically until no further material passes any of the sieves (see note). Record the
mass of material retained on each sieve and the mass passing the 2 mm aperture sieve.
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The total mass of the fractions should be within 1 % of m or m , as appropriate. If it is not, then check for sieve
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damage, and discard sieves as appropriate (note in 7.2.3).
Sieve equipment performance should be verified against a suitable test material, e.g. standard particle reference
materials, ballotini, at intervals of one month. The results of this check shall be recorded.
NOTE — For practical purposes, it is usual to choose a standard sieve shaking time which gives an acceptable degree of
sieving efficiency with a wide range of soil materials. The minimum recommended period is 10 min.
Table 1 — Mass of soil sample to be taken for sieving
Maximum size of material forming >10% of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
63 50
50 35
37,5 15
28 6
20 2
14 1
10 0,5
6,3 0,5
5 0,2
2 or smaller 0,1
Table 2 — Maximum mass of material to be retained on each test sieve at the completion of sieving
Maximum mass
kg
Test sieve aperture Sieve diameter
mm
mm 450 300 200
50 10 4,5
37,5 8 3,5
28 6 2,5
20 4 2,0
14 3 1,5
10 2 1,0
6,3 1,5 0,75
5 1,0 0,5
3,35 0,3
2 0,2
1,18 0,1
0,6 0,075
0,425 0,075
0,3 0,05
0,212 0,05
0,15 0,04
0,063 0,025
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7.4 Calculation and expression of results
For the material retained by the 20 mm and larger aperture sieves, calculate the proportion by mass retained by
each sieve as a proportion of m . For example:
proportion retained on the 20 mm sieve = [m(20 mm)]/m
For the material passing the 20 mm sieve, multiply the mass of material passing each sieve by , and calculate
m /m
2 3
this as a proportion of m . For example:
proportion retained on the 6,3 mm sieve = m(6,3 mm)[(m /m )/m ]
2 3 1
Present the results as a table showing, to two significant figures, the proportion by mass retained on each sieve,
and the proportion passing the 2 mm sieve. The data shall also be used to construct a cumulative distribution curve
(Figure 1).
8 Wet sieving and sedimentation (material < 2 mm)
8.1 General
This clause specifies the procedure (see figure 2) for the determination of the particle size distribution of the
material passing the 2 mm aperture sieve down to <0,002 mm equivalent spherical diameter (see note). In order to
ensure that primary particles are measured rather than loosely bonded aggregates, organic matter and salts are
removed, especially sparingly soluble salts such as gypsum which would otherwise prevent dispersion and/or
promote flocculation of the finer soil particles in suspension (8.6), and a dispersing agent is added (8.8). These
procedures are required in this International Standard, and their omission shall invalidate its application. Sometimes
iron oxides, and carbonates, especially of calcium and/or magnesium, are also removed. Preferred procedures for
the removal of these compounds are given in the note in 8.7. The removal of any compound shall be recorded in the
test report (clause 10).
NOTE — Gravitational sedimentation can give a value for the total amount of material <0,002 mm equivalent spherical
diameter. However, the method cannot be used to divide this class further with reliability, as particles less than about 0,001 mm
equivalent spherical diameter can be kept in suspension almost indefinitely by Brownian motion [1].
8.2 Apparatus
The apparatus specified hereafter is sufficient to deal with one sample. Clearly it is more efficient to work in batches.
Experience has shown [9] that one operator can process up to 36 samples in a batch at a time given sufficient
apparatus and space, especially if calculations are dealt with by a computer.
8.2.1 Sampling pipette of a pattern similar to that in Figure 3 [4], the chief requirement being that the smallest
practicable zone of sedimenting suspension shall be sampled. The pipette shall be of not less than 10 ml volume
and shall be held in a frame so that it can be lowered to a fixed depth within a sedimentation tube (Figure 4).
NOTE — Experience suggests that a pipette with an upper volume of 50 ml is more than sufficient for most purposes. A 25 ml
volume pipette is a convenient compromise for routine analysis, but a smaller volume pipette will be found sufficient for soils
with down to about 10 % mass fraction <0,063 mm equivalent spherical diameter. Below this amount, greater precision is likely
to be obtained with a larger volume pipette.
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Figure 1 — Particle size distribution chart
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Figure 2 — Flow chart
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Dimensions in millimetres
1 Bulb capacity 125 ml approx.
2 Pipette and changeover cock capacity ~ 10 ml.
NOTE — This design has been found satisfactory, but alternative designs may be used.
Figure 3 — Sampling pipette for sedimentation test
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A and B 125 ml bulb funnel with stopcock G Sampling pipette
C Safety bulb suction inlet tube H Sedimentation tube
D Safety bulb D, F and G are joined to three-way stopcock E
F Outlet tube
1 Scale graduated in millimetres 3 Sliding panel
2 Clamps 4 Constant-temperature bath
NOTE — This design has been found satisfactory, but alternative designs may be used.
Figure 4 — Arrangement for lowering sampling pipette into soil suspension
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8.2.2 Constant temperature room or bath, which can be maintained at between 20 °C and 30 °C ± 0,5 °C. If a
bath is used, it shall accept a sedimentation tube immersed to the 500 ml mark, and shall not vibrate the contents of
the tube. Similarly, if a room is used, it, and its furniture, shall be constructed so that activity does not cause the
tubes and their contents to vibrate.
NOTE — This temperature range has been chosen to allow for the difficulties of maintaining one specified temperature in
different parts of the world. In addition, the lower temperature gives sedimentation times that fit well into an average working
day, whilst the upper temperature still allows for a sensible settling time for the fraction 0,063 mm equivalent spherical diameter
(clause 4, Table 3).
Table 3 — Pipette sampling times and d (for a particle density of 2,65 Mg/m )
p
at a sampling depth of 100 mm ± 1 mm at different temperatures
Times, after mixing, of starting sampling operation
st 1) nd rd st
Temperature 1 sample 2 sample 3 sample 4 sample
°C min s min s min s h min s
20 0 56 4 38 51 35 7 44 16
21 0 54 4 32 50 27 7 34 4
22 0 53 4 26 49 19 7 23 53
23 0 52 4 19 48 8 7 13 13
24 0 51 4 13 47 0732
25 049 4 745 52 6 52 50
26 0 48 4 2 44 536442
27 0 47 3 57 43 58 6 35 42
28 0 46 3 52 42 59 6 26 53
29 0 45 3 47 42 3 6 18 33
30 0 44 3 41 41 5 6 9 45
d (mm) 0,063 0,020 0,006 0,002
p
1) Sampling depth 200 mm ± 1 mm to allow adequate time for the stabilization of the suspension after mixing.
8.2.3 Two glass sedimentation tubes, without pouring lips, of approximate internal diameter 50 mm, and overall
length 350 mm, graduated at 500 ml volume, and with either rubber bungs to fit, or a stirrer.
8.2.4 Stirrer of noncorrodible material, as in Figure 5.
8.2.5 Five glass weighing vessels, with masses known to the nearest 0,000 1 g.
8.2.6 Mechanical shaker capable of keeping 30 g of soil in suspension in 150 ml of liquid. A device which rotates
the container end-over-end at 30 revolutions/min to 60 revolutions/min is suitable. The vigorous end-to-end type of
shaker, and the horizontal rotary shaker are both unsuitable, and neither shall be used (see note in 8.9).
8.2.7 Test sieves complying with ISO 565, ISO 3310-1 and ISO 3310-2, having apertures of 2 mm and 0,063 mm,
plus two intermediate sieves. The test report shall state which apertures are used. Round-hole sieves shall not be
used.
NOTE — The choice of the sieve of aperture 0,063 mm given here is for illustration, but accords with the widespread use of
this particle size to define the upper boundary of the silt fraction. Local requirements may decide on another aperture. The
choice of apertures for the intermediate sieves is a matter for local knowledge, but experience suggests that sieves of aperture
close to 0,2 mm and 0,1 mm are useful for a very wide range of soils.
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Dimensions in millimetres
Prepare a stirrer as shown, suitable materials being
a) brass or aluminium,
b) Perspex/Plexiglas
c) a section of a rubber stopper fitted onto a glass rod, etc.
Figure 5 — Stirrer; perforated stopper fitted onto glass rod, for example
8.2.8 Suitable sample divider (clause 6).
8.2.9 Balance, capable of weighing to an accuracy of within ± 0,000 1 g.
capable of maintaining a temperature between 105 °C and 110 °C.
8.2.10 Drying oven,
8.2.11 Stop clock, readable to 1 s.
8.2.12 Desiccator containing anhydrous silica gel (preferably of the self-indicating type), capable of holding the
five weighing vessels. The desiccant shall be inspected daily and dried at between 105 °C and 110 °C when no
longer effective.
8.2.13 A 650 ml tall-form glass beaker with cover glass to fit, or a 300 ml centrifuge bottle with a leakproof cap.
NOTE — This apparatus is used for chemical pretreatment, a constant problem during which is the adhesion of very fine
particles to glass. The problem is much reduced if the treatment is carried out in a polycarbonate or polysulfone centrifuge
bottle. Both materials will withstand repeated heating to 120 °C and are resistant to hydrogen peroxide and common dispersing
agents. Their use can also save significant amounts of operator time.
8.2.14 Centrifuge, capable of holding the 300 ml centrifuge bottles (see 8.8).
8.2.15 100 ml measuring cylinder.
8.2.16 25 ml pipette.
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8.2.17 Glass filter funnel capable of holding the 0,063 mm sieve.
8.2.18 Wash bottle containing water (8.3).
8.2.19 Rod, of glass or strong plastic, 150 mm to 200 mm long and at least 4 mm in diameter, with a rubber sleeve
at one end.
8.2.20 Electric hotplate, capable of maintaining a temperature between 105 °C and 110 °C.
NOTE — A hotplate is essential if polymer centrifuge bottles are used for the chemical pretreatment, but Bunsen, gauze and
tripod are sufficient if glass beakers are used.
8.2.21 Suction device similar to that shown in Figure 6 is useful, but not essential.
1 To vacuum 3 Pasteur pipette or similar
2 Flexible tube 4 Reservoir (5 l or 10 l)
Figure 6 — Sketch of suction device
8.2.22 Sieve brush.
8.2.23 Electrical conductivity meter accurate to 0,1 dS/m.
8.3 Reagents
All reagents shall be of recognized analytical grade. Use water conforming to class 2 of ISO 3696, i.e. having an
electrical conductivity no greater than 0,1 dS/m at 25 °C at the time of use.
8.3.1 Hydrogen peroxide solution, 30 % volume fraction.
NOTE — A 30 % volume fraction solution is one which will yield 30 ml of gaseous oxygen from 100 ml of solution (under
standard conditions of temperature and pressure) upon reduction to water either by chemical means, or by boiling.
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8.3.2 Solution of a dispersing agent.
The most widely used is that prepared by dissolving 33 g of sodium hexametaphosphate and 7 g of anhydrous
sodium carbonate in water to make 1 l of solution. This is the preferred dispersant. Store away from strong sunlight,
and preferably in a dark bottle. Record the date of preparation on the bottle. The solution is unstable and shall be
replaced after one month.
Buffered sodium hexametaphosphate is commonly referred to in the literature as "Calgon". This is a trade name.
The substance sold as such is often not the reagent described in this subclause, is of variable composition, and
shall not be used as a dispersing agent in the method given in this International Standard [11].
It is permissible to use other dispersing agents (see note), the choice of which shall be recorded in the test report
(clause 10). Whichever dispersant proves to be the most suitable for a particular soil, it is essential that the
suspension is examined visually to ensure that effective dispersion has occurred and that the dispersed suspension
is stable, i.e. that no flocculation has, or is, occurring. This inspection shall be carried out for each and every
sample.
NOTE — The sodium carbonate buffers the solution, and the suspension of the soil, to about pH 9,8. This dispersing agent
has been found successful with a very wide range of soils. However, if there are signs that dispersion is ineffective, consider
firstly that flocculating salts might be present (see 8.8). If dispersion is still unsuccessful after removal of salts, then other
dispersing agents should be considered. A very effective, but less widely used dispersing agent, is prepared by replacing the
sodium carbonate with 20 % volume fraction ammonia solution, in the ratio of 5 ml ammonia solution to 150 ml of the
hexametaphosphate solution. There are many other dispersing agents [2]. Whichever is chosen, considerable investigation will
be required to establish its effectiveness. It should be remembered that some soils show fewer problems of dispersion if
analysed without drying (Annex A). Some soils derived from recent volcanic deposits will disperse more effectively in an acid
medium [12].
8.3.3 Octan-2-ol or a similar volatile antifoaming agent.
NOTE — Octan-2-ol is highly effective and relatively long-lasting. Ethanol or methanol can also be used, but the use of
pentan-2-ol (amyl alcohol) is discouraged because it is potentially addictive.
8.4 Calibrations
8.4.1 Sampling pipette (Figure 4)
Clean and dry the pipette thoroughly and immerse the tip in water held at the same temperature as that of the
constant-temperature environment (8.2.2). By means of a tube attached to C, draw water into the pipette above E.
Drain off the water above E through F. Drain the pipette into a weighing bottle of known mass, and determine the
new mass. From the known masses calculate the internal volume of the pipette. Repeat this exercise three times
and take the average of the three volumes as the internal volume of the pipette to the nearest 0,05 ml (V ml).
c
8.4.2 Dispersing agent correction
Follow this procedure each time a new batch of dispersing agent is prepared.
Pipette 25 ml of dispersing agent solution into one of the glass sedimentation tubes, and fill the tube to the 500 ml
mark with water. Mix the contents of the tube thoroughly. Place the tube in the constant temperature environment,
and leave the tube for at least 1 h. Between any of the times at which samples may be taken from the sampling tube
(Table 3), take a sample (V ml) of the dispersing agent solution from the sedimentation tube using the sampling
c
pipette. Drain the pipette into a weighing vessel of known mass, and dry the contents of the vessel between 105 °C
and 110 °C. Allow the vessel to cool in the desiccator and determine the mass of the residue in the vessel to
0,000 1 g (m ).
r
NOTE — The minimum temperature equilibration period in the water bath is 1 h, but if a large number of tubes is placed in a
bath equilibration will take at least 4 h. In such cases it is advantageous to arrange the work so that equilibration takes place
overnight. Equilibration will be quicker if the supply of water used to fill up the tubes is kept at, or near to, the same temperature
as the constant-temperature environment.
8.5 The test sample
The test sample shall be taken from the material passing a 2 mm aperture sieve (clause 6 and 7.2) and weighed to
the nearest 0,001 g (m ). The mass of test sample depends on the type of soil. Approximately 30 g for a sandy soil
s
and 10 g for a clay soil are appropriate for pipette analysis, with proportionate masses for soils intermediate to these
©
ISO
extremes. For the hydrometer method (Annex B), take twice this amount of material. Place the test sample in either
the 650 ml glass beaker or the 300 ml centrifuge bottle (8.2.13 and its note).
NOTE — Highly organic soils contain relatively little mineral matter. It might be necessary to take up to 100 g of such soils in
order to obtain sufficient mineral matter for a reliable analysis of the particle size distribution of this component. Such a large
amount of organic material should be apportioned between several vessels for ease of operation, with combination of the
mineral residues at a later stage.
8.6 Destruction of organic matter
Destroy the organic matter with hydrogen peroxide solution as follows. Add approximately 30 ml of water to the test
sample and allow it to become thoroughly wet (see note 1 below). Add 30 ml of 30 % volume fraction hydrogen
peroxide solution, and mix the contents of the vessel very gently using the glass or plastic rod. A vigorous reaction
can cause foaming of the sample mixture. This can be controlled by adding a few millilitres of octan-2-ol. Allow any
vigorous reaction to subside.
WARNING — Carry out this step with caution. Hydrogen peroxide can decompose violently with some
forms of organic matter, manganese compounds and finely-particulate iron sulfides, all of which can occur
in soil. Do not examine the reaction by looking into the top of the vessel, Do not accelerate an apparently
slow reaction by heating or addition of more hydrogen peroxide.
If using the 650 ml beaker, cover with the cover glass and leave overnight. Place the vessel on the hotplate or
bunsen burner, as appropriate (8.2.20) and warm gently. Control any foaming with octan-2-ol as before, and stir the
contents frequently. Do not allow the contents to dry out, adding more water if necessary. Bring the suspension to a
gentle boil and heat until all signs of bubbling due to decomposition of hydrogen peroxide have ceased. If there is
still undecomposed organic matter, remove the vessel from the heat, allow it to cool and repeat the treatment with
hydrogen peroxide. Highly organic soils will need several such treatments, the products of the reaction being
removed after every 2 or 3 treatments before continuing with more peroxide.
If destruction of organic matter has been carried out in a centrifuge bottle, bring the volume of the contents to
between 150 ml and 200 ml by addition of water. If a glass beaker has been used, then transfer the contents to a
centrifuge bottle, taking care to remove all traces of material from the sides of the beaker by means of the rubber
sleeve on the glass or plastic rod. Again, the final volume should be 150 ml to 200 ml. Centrifuge the bottle so as to
obtain a clear supernatant [15 min at a minimum relative centrifugal force (RCF) of 400g is recommended], and
decant the latter or remove by means of the suction device. Repeat the treatment until the supernatant is colourless
or nearly so.
NOTE 1 Dry organic materials are often strongly hydrophobic, in which case the addition of a few drops of octan-2-ol can be
beneficial.
If a centrifuge is not available, the mineral residues may be flocculated by adding 25 ml of 1 mol/l calcium chloride
solution. Stir thoroughly, bring to about 250 ml with water, allow to stand until the supernatant is clear, then siphon
or decant this from the residue. Add another 250 ml of water and repeat the washing procedure until the dark
residues of the decomposed organic matter have gone. Check that the electrical conductivity of the washings is
below 0,4 dS/m before attempting to disperse the residue (8.8).
Another alternative is to filter the residue from the oxidation step on a hardened, high wet-strength filter paper
(2,7 μm pore size is suitable), followed by thorough washing with water by means of the wash-bottle. It is essential
to observe the filtrate closely to see that no soil is lost. If particles pass through the filter paper, return the filtrate to
the container, add calcium chloride solution to the suspension as above, stir and refilter.
If flocculation with calcium chloride, or filtration are ineffective in preventing loss of fine soil particles, then a few
drops of a 60 g/l aluminium sulfate solution can be stirred into the soil suspension. The absolute minimum of
aluminium sulfate shall be used, as excess could cause problems in the subsequent dispersion of the soil.
NOTE 2 Lignified (woody) residues of plants are extremely difficult to decompose, and their complete destruction is often
impossible. Such fragments are usually regarded as decomposed when they have lost all traces of dark colour.
Transfer the washed residue quantitatively to a centrifuge bottle. In all cases, it is not essential for the supernatant
to be absolutely colourless, so long as it is obvious that the bulk of the dark decomposition products of the organic
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ISO
matter have been removed, but the solution shall be clear. The use of calcium chloride solution or aluminium sulfate
solution, in conjunction with filtration, decantation, suction or siphoning, shall be recorded on the test report
(clause 10).
8.7 Removal of soluble salts and gypsum
After removal of the residues following the destruction of organic matter, add sufficient water to the soil in the
centrifuge bottle so that the soil:water ratio is between 1:4 and 1:6 by volume. Shake the contents of the bottle
vigorously so that all the sediment is in suspension; then shake for 1 h on the end-over-end shaking machine.
Centrifuge to obtain a clear supernatant and measure its electrical conductivity (E ). If the latter is < 0,4 dS/m,
c
soluble salts and gypsum are not present in significant amounts. If the value of the E is > 0,4 dS/m, then remove
c
the supernatant in which the E was measured. Add 250 ml of water to the soil residue, cap the bottle and shake on
c
the end-over-end shaking machine for 1 h. Centrifuge to obtain a clear supernatant and measure the E again. If it
c
is < 0,4 dS/m, soluble salts and gypsum have been removed to an extent sufficient not to interfere in the dispersion
(8.8). If the E is > 0,4 dS/m, repeat the washing procedure until the E of the supernatant is < 0,4 dS/m. Record the
c c
removal of gypsum in the test report (clause 10).
Whilst the removal of soluble salts and gypsum is obligatory, that of iron (and associated aluminium) oxides, and of
carbonates is not (see note below). The removal of these compounds is a matter for local decision, but if done, the
preferred procedures are as follows. Iron oxides are removed by shaking the soil overnight with 40 g/l sodium
dithionite in ca. 0,3 mol/l sodium acetate solution buffered to pH 3,8 with acetic acid, in the ratio of 1 part soil to 40
parts of solution, both by volume.
Very iron-rich soils usually need several treatments. Magnetite is not affected by this procedure [7]. In certain soils,
especially those developed from recent volcanic deposits, this reagent can remove large quantities of aluminium as
well as iron. Calcium and magnesium carbonates are removed by treating the soil with the minimum possible
excess of aqueous hydrochloric acid.
The following procedure has been found to be applicable to a wide range of soils, and is best applied to the soil after
the removal of organic matter (8.6). Where the carbonate content is greater than about 2 % mass fraction, add to
the washed, centrifuged soil (above) 4 ml of 1 mol/l hydrochloric acid for each percent of carbonate, plus an excess
of 25 ml of acid. Make up to about 250 ml with water, and place the suspension on the water bath at about 80 °C for
15 min, stirring the suspension from time to time. Remove from the water bath and leave the suspension to stand
overnight. If the soil flocculates sufficiently to leave a perfectly clear supernatant, then this can be siphoned off or
decanted, otherwise centrifugation (8.6) and decantation will be necessary. Repeat the washing and decantation
with water until the E of the supernatant is less than 0,4 dS/m. If the carbonate content is less than about 2 % mass
c
fraction, then only an initial 25 ml of 1 mol/l hydrochloric acid solution is required. However, there is then the risk
that there will be insufficient calcium in solution to give good flocculation. It is recommended, therefore, that 20 ml of
1 mol/l calcium chloride solution is added at the same time as the acid. The rest of the procedure is identical for
both situations. If magnesium carbonates are present in substantial amounts, then the treatment can be lengthy.
Hot hydrochloric acid shall not be used in soils containing significant amounts of chlorite, as this can dissolve.
Removal of iron/aluminium oxides and/or carbonates shall be recorded in the test report (clause 10).
NOTE — Because of the slowness of the procedure and the difficulty of quantitative recovery of the residue, removal of
carbonates is not normally a routine procedure in the determination of particle size distribution.
8.8 Dispersion
Add sufficient water to the centrifuge bottle
...
oSIST ISO 11277:2006
oSIST ISO 11277:2006
INTERNATIONAL ISO
STANDARD 11277
First edition
1998-05-15
Soil quality — Determination of particle size
distribution in mineral soil material —
Method by sieving and sedimentation
Qualité du sol — Détermination de la répartition granulométrique de la
matière minérale des sols — Méthode par tamisage et sédimentation
A
Reference number
oSIST ISO 11277:2006
Contents Page
1 Scope. 1
2 Normative references. 1
3 Terminology and symbols. 2
4 Principle . 2
5 Field sampling . 4
6 Sample preparation. 4
7 Dry sieving . 4
8 Wet sieving and sedimentation. 6
9 Precision . 19
10 Test report. 19
Annex A: Determination of particle size distribution of mineral
soil material that is not dried prior to analysis . 20
Annex B: Determination of particle size distribution of mineral
soils by a hydrometer method following destruction
of organic matter. 23
Annex C: Bibliography. 30
© ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet central@iso.ch
X.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
ii
oSIST ISO 11277:2006
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ISO ISO 11277:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work of
preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 11277 was prepared by Technical Committee
ISO/TC 190, Soil quality, Subcommittee SC 5, Physical methods.
Annexes A and B form an integral part of this International Standard.
Annex C is for information only.
iii
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Introduction
The physical and chemical behaviour of soils is controlled in part by the
amounts of mineral particles of different sizes in the soil. The subject of this
International Standard is the quantitative measurement of such amounts
(expressed as a proportion or percentage of the total mass of the mineral
soil), within stated size classes.
The determination of particle size distribution is affected by organic matter,
soluble salts, cementing agents (especially iron compounds), relatively
insoluble substances such as carbonates and sulfates, or combinations of
these. Some soils change their behaviour to such a degree upon drying,
that the particle size distribution of the dried material bears little or no
relation to that of the undried material encountered under natural
conditions. This is particularly true of soils rich in organic matter, those
developed from recent volcanic deposits, some highly weathered tropical
soils, and soils often described as “cohesive” [6]. Other soils, such as the
so-called "sub-plastic" soils of Australia, show little or no tendency to
disperse under normal laboratory treatments, despite field evidence of a
large clay content.
The procedures given in this International Standard recognize these kinds
of differences between soils from different environments, and the
methodology presented is designed to deal with them in a structured
manner. Such differences in soil behaviour can be very important, but
awareness of them depends usually on local knowledge. Given that the
laboratory is commonly distant from the site of the field operation, the
information supplied by field teams becomes crucial to the choice of an
appropriate laboratory procedure. This choice can be made only if the
laboratory is made fully aware of this background information.
All procedures in this International Standard should be carried out by
competent, trained persons, with adequate supervision. Attention is drawn
to certain known hazards, but it is essential that users follow safe working
practices. If in any doubt, seek professional advice.
It is essential that users of this International Standard read all of it
before commencing any operation, as failure to note certain points
will lead to incorrect analysis, and could be dangerous.
iv
oSIST ISO 11277:2006
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INTERNATIONAL STANDARD ISO ISO 11277:1998(E)
Soil quality — Determination of particle size distribution in mineral
soil material — Method by sieving and sedimentation
1 Scope
This International Standard specifies a basic method of determining particle size distribution applicable to a wide
range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with
the less common soils mentioned in the introduction. This International Standard has been developed largely for
use in the field of environmental science, and its use in geotechnical investigations is something on which
professional advice might be required.
A major objective of this International Standard is the determination of enough size fractions to enable the
construction of a reliable particle size distribution curve.
This International Standard does not apply to the determination of the particle size distribution of the organic
components of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It should also
be realized that the chemical pretreatments and mechanical handling stages in this International Standard could
cause disintegration of weakly cohesive particles that, from field inspection, might be regarded as primary particles,
even though such primary particles could be better described as aggregates. If such disintegration is undesirable,
then this International Standard should not be used for the determination of the particle size distribution of such
weakly cohesive materials.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 565:1990, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings.
ISO 3310-1:1990, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth.
ISO 3310-2:1990, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal
plate.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
ISO 11464:1994, Soil quality — Pretreatment of samples for physico-chemical analyses.
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3 Terminology and symbols
3.1 Terminology
Particles within particular size ranges or classes are commonly described as cobbles, gravel, coarse sand, silt, etc.
The meaning of such trivial names differs between countries, and in some cases there are no exact translations of
such words from one language to another; for example, the Dutch word "zavel" has no equivalent in English. The
only fraction for which there appears to be common agreement is clay, which is defined as material of less than
0,002 mm equivalent spherical diameter [1, 6]. Such trivial names shall not be used in describing the results of
particle size determination according to this International Standard. Phrases such as ".passing a 20 mm aperture
sieve." or ".less then 0,063 mm equivalent spherical diameter." shall be used instead. If trivial names must be
used, for example to cross-reference to another (inter-)national standard, then the trivial name should be defined
explicitly, so as to remove any doubt as to the meaning intended, e.g. silt (0,063 mm to 0,002 mm equivalent
spherical diameter) (clause 4 and, for example, [3]). Further, it is common to use the word 'texture' to describe the
results of particle size distribution measurements, e.g. 'the particle size of this soil is of clay texture'. This is incorrect
as the two concepts are different, and the word 'texture' shall not be used in the test report (clause 10) to describe
the results obtained by use of this International Standard.
It is common to refer to sieves as having a particular mesh-size or mesh number. These are not the same as the
sieve aperture, and the relationship between the various numbers is not immediately obvious. The use of mesh
numbers as a measurement of particle size is difficult to justify, and shall not be used in reporting the results of this
International Standard.
3.2 Symbols
The following symbols are found throughout the text and, where appropriate, units and quantities are as given below
(SI convention is followed for common units e.g. g = gram; m = metre; mm = millimetre; s = second, etc.).
Mg megagram (10 g)
mPa millipascal
t is the settling time, in seconds, of a particle of diameter d ;
p
η is the dynamic viscosity of water at the test temperature (see Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65; note in clause 4);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken as 1,00;
w
note in clause 4);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981);
d is the equivalent spherical diameter of the particle of interest, in millimetres;
p
4 Principle
Particle size distribution is determined by a combination of sieving and sedimentation, starting from air-dried soil [6]
(see note below). A method for undried soil is given in Annex A. Particles not passing a 2 mm aperture sieve are
determined by dry sieving. Particles passing such a sieve, but retained on a 0,063 mm aperture sieve, are
determined by a combination of wet and dry sieving, whilst particles passing the latter sieve are determined by
sedimentation. The pipette method is preferred. A hydrometer method is given in Annex B. A combination of sieving
and sedimentation enables construction of a continuous particle size distribution curve.
The key points in this procedure are summarized as a flow chart in Figure 2. This International Standard requires
that the proportions of fractions separated by sedimentation and sieving be determined from the masses of such
fractions obtained by weighing. Other methods of determining the mass of such fractions rely on such things as the
oSIST ISO 11277:2006
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interaction of particles with electromagnetic radiation or electrical fields [1]. There are often considerable difficulties
in relating the values obtained by different methods, one to another, for the same sample. It is one of the intentions
of this International Standard that close adherence to its details should help minimize interlaboratory variation in the
determination of the particle size distribution of mineral soils. Therefore the proportions of fractions shall be
determined only by weighing. If this is not the method used, then compliance with this International Standard cannot
be claimed in the test report (clause 10).
Both the pipette and hydrometer methods assume that the settling of particles in the sedimentation cylinder is in
accordance with Stokes' Law [1, 6, 9], and the constraints that this implies, namely:
a) the particles are rigid, smooth spheres;
b) the particles settle in laminar flow i.e. the Reynolds Number is less than about 0,2. This constraint sets an upper
equivalent spherical particle diameter (below) slightly greater than 0,06 mm for Stokesian settling under
gravity [1];
c) the suspension of particles is sufficiently dilute to ensure that no particle interferes with the settling of any other
particle;
d) there is no interaction between particle and fluid;
e) the diameter of the suspension column is large compared to the diameter of the particle, i.e. the fluid is of 'infinite
extent';
f) the particle has reached its terminal velocity;
g) the particles are of the same relative density.
Thus, the diameter of a particle is defined in terms of the diameter of a sphere whose behaviour in suspension
matches that of the particle. This is the concept of . It is the principle upon which the
equivalent spherical diameter
expression of the diameter of particles, as derived from sedimentation, is based in this International Standard.
Stokes' Law can be written, for the purposes of this International Standard, in the form:
t = 18ηh/[(ρ — ρ )gd ]
s w p
where
t is the settling time, in seconds, of a particle of diameter d (below);
p
η is the dynamic viscosity of water at the test temperature (Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65; see note);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken as 1,00;
w
see note);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981);
d is the equivalent spherical diameter of the particle of interest, in millimetres;
p
NOTE — It is realized that there are considerable differences between the densities of soil particles, but for the purposes of
this International Standard it is assumed that the mean particle density is that of quartz, i.e. 2,65 Mg/m [10], as this is the
3 3
commonest mineral in a very wide range of soils. The density of water is 0,9982 Mg/m and 0,9956 Mg/m at 20 °C and 30 °C,
respectively [8]. Given the effect of the addition of a small amount of dispersant (8.3.2), the density of water is taken as
1,0000 Mg/m over the permitted temperature range of this International Standard (8.2.2). Further, for routine use, it is
recommended that the sampling times be converted to minutes and/or hours, as appropriate, to lessen the risk of error
(Table 3).
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5 Field sampling
The mass of sample taken in the field shall be representative of the particle size distribution, especially if the
amount of the larger particles is to be determined reliably. Table 1 gives recommended minimum masses.
6 Sample preparation
Samples shall be prepared in accordance with the methods given in ISO 11464.
NOTE — For many purposes, particle size distribution is determined only for the fraction of the soil passing a 2 mm aperture
sieve. In this case, the test sample (8.5) may be taken either according to the procedures in ISO 11464 or from the material
passing a 2 mm aperture sieve according to 7.2.
7 Dry sieving (material > 2 mm)
7.1 General
The procedure specified in this clause applies to material retained on a 2 mm aperture sieve. Table 2 gives the
maximum mass which shall be retained on sieves of different diameters and apertures. If more than this amount of
material is retained, then it shall be subdivided appropriately, and resieved.
7.2 Apparatus
7.2.1 Test sieves, with apertures which comply with ISO 565, and with well-fitting covers and receivers.
The full range of sieves appropriate to the largest particle(s) present should be used (Table 1; note in 7.2.3). The
apertures chosen shall be stated in the test report (clause 10). The accuracy of the sieves shall be verified monthly
against a set of master sieves kept for this purpose, using an accepted method such as particle reference materials,
microscopy etc. [1] depending on the sieve aperture. Tolerances shall meet the requirements of ISO 3310-1 and
ISO 3310-2. Sieves that do not meet these specifications shall be discarded. A record shall be kept of such testing.
Brass sieves are particularly liable to splitting and distortion, and steel sieves are strongly recommended for the
larger apertures.
Special care shall be taken to ensure that covers and receivers do not leak. Sieves shall be inspected weekly when
in regular use, and on every occasion if used less often. A record shall be kept of such inspections. Round-hole
sieves shall not be used.
7.2.2 Balance, capable of weighing to an accuracy of within ± 0,5 g.
7.2.3 Mechanical sieve shaker
NOTE — It is usually impracticable to sieve mechanically at sieve apertures much greater than 20 mm, unless very heavy-
duty equipment is available. Mechanical sieve shaking is essential to sieve efficiency at smaller apertures.
7.2.4 A sieve brush and a stiff brush.
7.3 Procedure
Weigh the dry test sample, prepared in accordance with ISO 11464, to the nearest 0,5 g (m ). Place the weighed
material on the 20 mm sieve, and by brushing the material gently over the sieve apertures with the stiff brush (to
remove any adhering soil), sieve the material. Take care not to detach any fragments from the primary particles.
Sieve the retained material on the nest of sieves of selected apertures (7.1.1), and record the amount retained on
each sieve to the nearest 0,5 g. Do not overload the sieves (Table 1), but sieve the material in portions if necessary.
Weigh the material passing the 20 mm aperture sieve (m ), or a suitable portion of it (m ) (Table 2) obtained by an
2 3
appropriate subsampling method (clause 6), and place this on a nest of sieves, the lowermost having an aperture of
2 mm. Shake the sieves mechanically until no further material passes any of the sieves (see note). Record the
mass of material retained on each sieve and the mass passing the 2 mm aperture sieve.
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The total mass of the fractions should be within 1 % of m or m , as appropriate. If it is not, then check for sieve
2 3
damage, and discard sieves as appropriate (note in 7.2.3).
Sieve equipment performance should be verified against a suitable test material, e.g. standard particle reference
materials, ballotini, at intervals of one month. The results of this check shall be recorded.
NOTE — For practical purposes, it is usual to choose a standard sieve shaking time which gives an acceptable degree of
sieving efficiency with a wide range of soil materials. The minimum recommended period is 10 min.
Table 1 — Mass of soil sample to be taken for sieving
Maximum size of material forming >10% of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
63 50
50 35
37,5 15
28 6
20 2
14 1
10 0,5
6,3 0,5
5 0,2
2 or smaller 0,1
Table 2 — Maximum mass of material to be retained on each test sieve at the completion of sieving
Maximum mass
kg
Test sieve aperture Sieve diameter
mm
mm 450 300 200
50 10 4,5
37,5 8 3,5
28 6 2,5
20 4 2,0
14 3 1,5
10 2 1,0
6,3 1,5 0,75
5 1,0 0,5
3,35 0,3
2 0,2
1,18 0,1
0,6 0,075
0,425 0,075
0,3 0,05
0,212 0,05
0,15 0,04
0,063 0,025
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7.4 Calculation and expression of results
For the material retained by the 20 mm and larger aperture sieves, calculate the proportion by mass retained by
each sieve as a proportion of m . For example:
proportion retained on the 20 mm sieve = [m(20 mm)]/m
For the material passing the 20 mm sieve, multiply the mass of material passing each sieve by , and calculate
m /m
2 3
this as a proportion of m . For example:
proportion retained on the 6,3 mm sieve = m(6,3 mm)[(m /m )/m ]
2 3 1
Present the results as a table showing, to two significant figures, the proportion by mass retained on each sieve,
and the proportion passing the 2 mm sieve. The data shall also be used to construct a cumulative distribution curve
(Figure 1).
8 Wet sieving and sedimentation (material < 2 mm)
8.1 General
This clause specifies the procedure (see figure 2) for the determination of the particle size distribution of the
material passing the 2 mm aperture sieve down to <0,002 mm equivalent spherical diameter (see note). In order to
ensure that primary particles are measured rather than loosely bonded aggregates, organic matter and salts are
removed, especially sparingly soluble salts such as gypsum which would otherwise prevent dispersion and/or
promote flocculation of the finer soil particles in suspension (8.6), and a dispersing agent is added (8.8). These
procedures are required in this International Standard, and their omission shall invalidate its application. Sometimes
iron oxides, and carbonates, especially of calcium and/or magnesium, are also removed. Preferred procedures for
the removal of these compounds are given in the note in 8.7. The removal of any compound shall be recorded in the
test report (clause 10).
NOTE — Gravitational sedimentation can give a value for the total amount of material <0,002 mm equivalent spherical
diameter. However, the method cannot be used to divide this class further with reliability, as particles less than about 0,001 mm
equivalent spherical diameter can be kept in suspension almost indefinitely by Brownian motion [1].
8.2 Apparatus
The apparatus specified hereafter is sufficient to deal with one sample. Clearly it is more efficient to work in batches.
Experience has shown [9] that one operator can process up to 36 samples in a batch at a time given sufficient
apparatus and space, especially if calculations are dealt with by a computer.
8.2.1 Sampling pipette of a pattern similar to that in Figure 3 [4], the chief requirement being that the smallest
practicable zone of sedimenting suspension shall be sampled. The pipette shall be of not less than 10 ml volume
and shall be held in a frame so that it can be lowered to a fixed depth within a sedimentation tube (Figure 4).
NOTE — Experience suggests that a pipette with an upper volume of 50 ml is more than sufficient for most purposes. A 25 ml
volume pipette is a convenient compromise for routine analysis, but a smaller volume pipette will be found sufficient for soils
with down to about 10 % mass fraction <0,063 mm equivalent spherical diameter. Below this amount, greater precision is likely
to be obtained with a larger volume pipette.
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Figure 1 — Particle size distribution chart
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Figure 2 — Flow chart
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Dimensions in millimetres
1 Bulb capacity 125 ml approx.
2 Pipette and changeover cock capacity ~ 10 ml.
NOTE — This design has been found satisfactory, but alternative designs may be used.
Figure 3 — Sampling pipette for sedimentation test
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A and B 125 ml bulb funnel with stopcock G Sampling pipette
C Safety bulb suction inlet tube H Sedimentation tube
D Safety bulb D, F and G are joined to three-way stopcock E
F Outlet tube
1 Scale graduated in millimetres 3 Sliding panel
2 Clamps 4 Constant-temperature bath
NOTE — This design has been found satisfactory, but alternative designs may be used.
Figure 4 — Arrangement for lowering sampling pipette into soil suspension
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8.2.2 Constant temperature room or bath, which can be maintained at between 20 °C and 30 °C ± 0,5 °C. If a
bath is used, it shall accept a sedimentation tube immersed to the 500 ml mark, and shall not vibrate the contents of
the tube. Similarly, if a room is used, it, and its furniture, shall be constructed so that activity does not cause the
tubes and their contents to vibrate.
NOTE — This temperature range has been chosen to allow for the difficulties of maintaining one specified temperature in
different parts of the world. In addition, the lower temperature gives sedimentation times that fit well into an average working
day, whilst the upper temperature still allows for a sensible settling time for the fraction 0,063 mm equivalent spherical diameter
(clause 4, Table 3).
Table 3 — Pipette sampling times and d (for a particle density of 2,65 Mg/m )
p
at a sampling depth of 100 mm ± 1 mm at different temperatures
Times, after mixing, of starting sampling operation
st 1) nd rd st
Temperature 1 sample 2 sample 3 sample 4 sample
°C min s min s min s h min s
20 0 56 4 38 51 35 7 44 16
21 0 54 4 32 50 27 7 34 4
22 0 53 4 26 49 19 7 23 53
23 0 52 4 19 48 8 7 13 13
24 0 51 4 13 47 0732
25 049 4 745 52 6 52 50
26 0 48 4 2 44 536442
27 0 47 3 57 43 58 6 35 42
28 0 46 3 52 42 59 6 26 53
29 0 45 3 47 42 3 6 18 33
30 0 44 3 41 41 5 6 9 45
d (mm) 0,063 0,020 0,006 0,002
p
1) Sampling depth 200 mm ± 1 mm to allow adequate time for the stabilization of the suspension after mixing.
8.2.3 Two glass sedimentation tubes, without pouring lips, of approximate internal diameter 50 mm, and overall
length 350 mm, graduated at 500 ml volume, and with either rubber bungs to fit, or a stirrer.
8.2.4 Stirrer of noncorrodible material, as in Figure 5.
8.2.5 Five glass weighing vessels, with masses known to the nearest 0,000 1 g.
8.2.6 Mechanical shaker capable of keeping 30 g of soil in suspension in 150 ml of liquid. A device which rotates
the container end-over-end at 30 revolutions/min to 60 revolutions/min is suitable. The vigorous end-to-end type of
shaker, and the horizontal rotary shaker are both unsuitable, and neither shall be used (see note in 8.9).
8.2.7 Test sieves complying with ISO 565, ISO 3310-1 and ISO 3310-2, having apertures of 2 mm and 0,063 mm,
plus two intermediate sieves. The test report shall state which apertures are used. Round-hole sieves shall not be
used.
NOTE — The choice of the sieve of aperture 0,063 mm given here is for illustration, but accords with the widespread use of
this particle size to define the upper boundary of the silt fraction. Local requirements may decide on another aperture. The
choice of apertures for the intermediate sieves is a matter for local knowledge, but experience suggests that sieves of aperture
close to 0,2 mm and 0,1 mm are useful for a very wide range of soils.
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Dimensions in millimetres
Prepare a stirrer as shown, suitable materials being
a) brass or aluminium,
b) Perspex/Plexiglas
c) a section of a rubber stopper fitted onto a glass rod, etc.
Figure 5 — Stirrer; perforated stopper fitted onto glass rod, for example
8.2.8 Suitable sample divider (clause 6).
8.2.9 Balance, capable of weighing to an accuracy of within ± 0,000 1 g.
capable of maintaining a temperature between 105 °C and 110 °C.
8.2.10 Drying oven,
8.2.11 Stop clock, readable to 1 s.
8.2.12 Desiccator containing anhydrous silica gel (preferably of the self-indicating type), capable of holding the
five weighing vessels. The desiccant shall be inspected daily and dried at between 105 °C and 110 °C when no
longer effective.
8.2.13 A 650 ml tall-form glass beaker with cover glass to fit, or a 300 ml centrifuge bottle with a leakproof cap.
NOTE — This apparatus is used for chemical pretreatment, a constant problem during which is the adhesion of very fine
particles to glass. The problem is much reduced if the treatment is carried out in a polycarbonate or polysulfone centrifuge
bottle. Both materials will withstand repeated heating to 120 °C and are resistant to hydrogen peroxide and common dispersing
agents. Their use can also save significant amounts of operator time.
8.2.14 Centrifuge, capable of holding the 300 ml centrifuge bottles (see 8.8).
8.2.15 100 ml measuring cylinder.
8.2.16 25 ml pipette.
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8.2.17 Glass filter funnel capable of holding the 0,063 mm sieve.
8.2.18 Wash bottle containing water (8.3).
8.2.19 Rod, of glass or strong plastic, 150 mm to 200 mm long and at least 4 mm in diameter, with a rubber sleeve
at one end.
8.2.20 Electric hotplate, capable of maintaining a temperature between 105 °C and 110 °C.
NOTE — A hotplate is essential if polymer centrifuge bottles are used for the chemical pretreatment, but Bunsen, gauze and
tripod are sufficient if glass beakers are used.
8.2.21 Suction device similar to that shown in Figure 6 is useful, but not essential.
1 To vacuum 3 Pasteur pipette or similar
2 Flexible tube 4 Reservoir (5 l or 10 l)
Figure 6 — Sketch of suction device
8.2.22 Sieve brush.
8.2.23 Electrical conductivity meter accurate to 0,1 dS/m.
8.3 Reagents
All reagents shall be of recognized analytical grade. Use water conforming to class 2 of ISO 3696, i.e. having an
electrical conductivity no greater than 0,1 dS/m at 25 °C at the time of use.
8.3.1 Hydrogen peroxide solution, 30 % volume fraction.
NOTE — A 30 % volume fraction solution is one which will yield 30 ml of gaseous oxygen from 100 ml of solution (under
standard conditions of temperature and pressure) upon reduction to water either by chemical means, or by boiling.
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8.3.2 Solution of a dispersing agent.
The most widely used is that prepared by dissolving 33 g of sodium hexametaphosphate and 7 g of anhydrous
sodium carbonate in water to make 1 l of solution. This is the preferred dispersant. Store away from strong sunlight,
and preferably in a dark bottle. Record the date of preparation on the bottle. The solution is unstable and shall be
replaced after one month.
Buffered sodium hexametaphosphate is commonly referred to in the literature as "Calgon". This is a trade name.
The substance sold as such is often not the reagent described in this subclause, is of variable composition, and
shall not be used as a dispersing agent in the method given in this International Standard [11].
It is permissible to use other dispersing agents (see note), the choice of which shall be recorded in the test report
(clause 10). Whichever dispersant proves to be the most suitable for a particular soil, it is essential that the
suspension is examined visually to ensure that effective dispersion has occurred and that the dispersed suspension
is stable, i.e. that no flocculation has, or is, occurring. This inspection shall be carried out for each and every
sample.
NOTE — The sodium carbonate buffers the solution, and the suspension of the soil, to about pH 9,8. This dispersing agent
has been found successful with a very wide range of soils. However, if there are signs that dispersion is ineffective, consider
firstly that flocculating salts might be present (see 8.8). If dispersion is still unsuccessful after removal of salts, then other
dispersing agents should be considered. A very effective, but less widely used dispersing agent, is prepared by replacing the
sodium carbonate with 20 % volume fraction ammonia solution, in the ratio of 5 ml ammonia solution to 150 ml of the
hexametaphosphate solution. There are many other dispersing agents [2]. Whichever is chosen, considerable investigation will
be required to establish its effectiveness. It should be remembered that some soils show fewer problems of dispersion if
analysed without drying (Annex A). Some soils derived from recent volcanic deposits will disperse more effectively in an acid
medium [12].
8.3.3 Octan-2-ol or a similar volatile antifoaming agent.
NOTE — Octan-2-ol is highly effective and relatively long-lasting. Ethanol or methanol can also be used, but the use of
pentan-2-ol (amyl alcohol) is discouraged because it is potentially addictive.
8.4 Calibrations
8.4.1 Sampling pipette (Figure 4)
Clean and dry the pipette thoroughly and immerse the tip in water held at the same temperature as that of the
constant-temperature environment (8.2.2). By means of a tube attached to C, draw water into the pipette above E.
Drain off the water above E through F. Drain the pipette into a weighing bottle of known mass, and determine the
new mass. From the known masses calculate the internal volume of the pipette. Repeat this exercise three times
and take the average of the three volumes as the internal volume of the pipette to the nearest 0,05 ml (V ml).
c
8.4.2 Dispersing agent correction
Follow this procedure each time a new batch of dispersing agent is prepared.
Pipette 25 ml of dispersing agent solution into one of the glass sedimentation tubes, and fill the tube to the 500 ml
mark with water. Mix the contents of the tube thoroughly. Place the tube in the constant temperature environment,
and leave the tube for at least 1 h. Between any of the times at which samples may be taken from the sampling tube
(Table 3), take a sample (V ml) of the dispersing agent solution from the sedimentation tube using the sampling
c
pipette. Drain the pipette into a weighing vessel of known mass, and dry the contents of the vessel between 105 °C
and 110 °C. Allow the vessel to cool in the desiccator and determine the mass of the residue in the vessel to
0,000 1 g (m ).
r
NOTE — The minimum temperature equilibration period in the water bath is 1 h, but if a large number of tubes is placed in a
bath equilibration will take at least 4 h. In such cases it is advantageous to arrange the work so that equilibration takes place
overnight. Equilibration will be quicker if the supply of water used to fill up the tubes is kept at, or near to, the same temperature
as the constant-temperature environment.
8.5 The test sample
The test sample shall be taken from the material passing a 2 mm aperture sieve (clause 6 and 7.2) and weighed to
the nearest 0,001 g (m ). The mass of test sample depends on the type of soil. Approximately 30 g for a sandy soil
s
and 10 g for a clay soil are appropriate for pipette analysis, with proportionate masses for soils intermediate to these
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extremes. For the hydrometer method (Annex B), take twice this amount of material. Place the test sample in either
the 650 ml glass beaker or the 300 ml centrifuge bottle (8.2.13 and its note).
NOTE — Highly organic soils contain relatively little mineral matter. It might be necessary to take up to 100 g of such soils in
order to obtain sufficient mineral matter for a reliable analysis of the particle size distribution of this component. Such a large
amount of organic material should be apportioned between several vessels for ease of operation, with combination of the
mineral residues at a later stage.
8.6 Destruction of organic matter
Destroy the organic matter with hydrogen peroxide solution as follows. Add approximately 30 ml of water to the test
sample and allow it to become thoroughly wet (see note 1 below). Add 30 ml of 30 % volume fraction hydrogen
peroxide solution, and mix the contents of the vessel very gently using the glass or plastic rod. A vigorous reaction
can cause foaming of the sample mixture. This can be controlled by adding a few millilitres of octan-2-ol. Allow any
vigorous reaction to subside.
WARNING — Carry out this step with caution. Hydrogen peroxide can decompose violently with some
forms of organic matter, manganese compounds and finely-particulate iron sulfides, all of which can occur
in soil. Do not examine the reaction by looking into the top of the vessel, Do not accelerate an apparently
slow reaction by heating or addition of more hydrogen peroxide.
If using the 650 ml beaker, cover with the cover glass and leave overnight. Place the vessel on the hotplate or
bunsen burner, as appropriate (8.2.20) and warm gently. Control any foaming with octan-2-ol as before, and stir the
contents frequently. Do not allow the contents to dry out, adding more water if necessary. Bring the suspension to a
gentle boil and heat until all signs of bubbling due to decomposition of hydrogen peroxide have ceased. If there is
still undecomposed organic matter, remove the vessel from the heat, allow it to cool and repeat the treatment with
hydrogen peroxide. Highly organic soils will need several such treatments, the products of the reaction being
removed after every 2 or 3 treatments before continuing with more peroxide.
If destruction of organic matter has been carried out in a centrifuge bottle, bring the volume of the contents to
between 150 ml and 200 ml by addition of water. If a glass beaker has been used, then transfer the contents to a
centrifuge bottle, taking care to remove all traces of material from the sides of the beaker by means of the rubber
sleeve on the glass or plastic rod. Again, the final volume should be 150 ml to 200 ml. Centrifuge the bottle so as to
obtain a clear supernatant [15 min at a minimum relative centrifugal force (RCF) of 400g is recommended], and
decant the latter or remove by means of the suction device. Repeat the treatment until the supernatant is colourless
or nearly so.
NOTE 1 Dry organic materials are often strongly hydrophobic, in which case the addition of a few drops of octan-2-ol can be
beneficial.
If a centrifuge is not available, the mineral residues may be flocculated by adding 25 ml of 1 mol/l calcium chloride
solution. Stir thoroughly, bring to about 250 ml with water, allow to stand until the supernatant is clear, then siphon
or decant this from the residue. Add another 250 ml of water and repeat the washing procedure until the dark
residues of the decomposed organic matter have gone. Check that the electrical conductivity of the washings is
below 0,4 dS/m before attempting to disperse the residue (8.8).
Another alternative is to filter the residue from the oxidation step on a hardened, high wet-strength filter paper
(2,7 μm pore size is suitable), followed by thorough washing with water by means of the wash-bottle. It is essential
to observe the filtrate closely to see that no soil is lost. If particles pass through the filter paper, return the filtrate to
the container, add calcium chloride solution to the suspension as above, stir and refilter.
If flocculation with calcium chloride, or filtration are ineffective in preventing loss of fine soil particles, then a few
drops of a 60 g/l aluminium sulfate solution can be stirred into the soil suspension. The absolute minimum of
aluminium sulfate shall be used, as excess could cause problems in the subsequent dispersion of the soil.
NOTE 2 Lignified (woody) residues of plants are extremely difficult to decompose, and their complete destruction is often
impossible. Such fragments are usually regarded as decomposed when they have lost all traces of dark colour.
Transfer the washed residue quantitatively to a centrifuge bottle. In all cases, it is not essential for the supernatant
to be absolutely colourless, so long as it is obvious that the bulk of the dark decomposition products of the organic
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matter have been removed, but the solution shall be clear. The use of calcium chloride solution or aluminium sulfate
solution, in conjunction with filtration, decantation, suction or siphoning, shall be recorded on the test report
(clause 10).
8.7 Removal of soluble salts and gypsum
After removal of the residues following the destruction of organic matter, add sufficient water to the soil in the
centrifuge bottle so that the soil:water ratio is between 1:4 and 1:6 by volume. Shake the contents of the bottle
vigorously so that all the sediment is in suspension; then shake for 1 h on the end-over-end shaking machine.
Centrifuge to obtain a clear supernatant and measure its electrical conductivity (E ). If the latter is < 0,4 dS/m,
c
soluble salts and gypsum are not present in significant amounts. If the value of the E is > 0,4 dS/m, then remove
c
the supernatant in which the E was measured. Add 250 ml of water to the soil residue, cap the bottle and shake on
c
the end-over-end shaking machine for 1 h. Centrifuge to obtain a clear supernatant and measure the E again. If it
c
is < 0,4 dS/m, soluble salts and gypsum have been removed to an extent sufficient not to interfere in the dispersion
(8.8). If the E is > 0,4 dS/m, repeat the washing procedure until the E of the supernatant is < 0,4 dS/m. Record the
c c
removal of gypsum in the test report (clause 10).
Whilst the removal of soluble salts and gypsum is obligatory, that of iron (and associated aluminium) oxides, and of
carbonates is not (see note below). The removal of these compounds is a matter for local decision, but if done, the
preferred procedures are as follows. Iron oxides are removed by shaking the soil overnight with 40 g/l sodium
dithionite in ca. 0,3 mol/l sodium acetate solution buffered to pH 3,8 with acetic acid, in the ratio of 1 part soil to 40
parts of solution, both by volume.
Very iron-rich soils usually need several treatments. Magnetite is not affected by this procedure [7]. In certain soils,
especially those developed from recent volcanic deposits, this reagent can remove large quantities of aluminium as
well as iron. Calcium and magnesium carbonates are removed by treating the soil with the minimum possible
excess of aqueous hydrochloric acid.
The following procedure has been found to be applicable to a wide range of soils, and is best applied to the soil after
the removal of organic matter (8.6). Where the carbonate content is greater than about 2 % mass fraction, add to
the washed, centrifuged soil (above) 4 ml of 1 mol/l hydrochloric acid for each percent of carbonate, plus an excess
of 25 ml of acid. Make up to about 250 ml with water, and place the suspension on the water bath at about 80 °C for
15 min, stirring the suspension from time to time. Remove from the water bath and leave the suspension to stand
overnight. If the soil flocculates sufficiently to leave a perfectly clear supernatant, then this can be siphoned off or
decanted, otherwise centrifugation (8.6) and decantation will be necessary. Repeat the washing and decantation
with water until the E of the supernatant is less than 0,4 dS/m. If the carbonate content is less than about 2 % mass
c
fraction, then only an initial 25 ml of 1 mol/l hydrochloric acid solution is required. However, there is then the risk
that there will be insufficient calcium in solution to give good flocculation. It is recommended, therefore, that 20 ml of
1 mol/l calcium chloride solution is added at the same time as the acid. The rest of the procedure is identical for
both situations. If magnesium carbonates are present in substantial amo
...
SLOVENSKI STANDARD
01-september-2006
Kakovost tal – Ugotavljanje porazdelitve velikosti delcev v mineralnem delu tal –
Metoda s sejanjem in usedanjem
Soil quality -- Determination of particle size distribution in mineral soil material -- Method
by sieving and sedimentation
Qualité du sol -- Détermination de la répartition granulométrique de la matière minérale
des sols -- Méthode par tamisage et sédimentation
Ta slovenski standard je istoveten z: ISO 11277:1998
ICS:
13.080.20 Fizikalne lastnosti tal Physical properties of soils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
INTERNATIONAL ISO
STANDARD 11277
First edition
1998-05-15
Soil quality — Determination of particle size
distribution in mineral soil material —
Method by sieving and sedimentation
Qualité du sol — Détermination de la répartition granulométrique de la
matière minérale des sols — Méthode par tamisage et sédimentation
A
Reference number
Contents Page
1 Scope. 1
2 Normative references. 1
3 Terminology and symbols. 2
4 Principle . 2
5 Field sampling . 4
6 Sample preparation. 4
7 Dry sieving . 4
8 Wet sieving and sedimentation. 6
9 Precision . 19
10 Test report. 19
Annex A: Determination of particle size distribution of mineral
soil material that is not dried prior to analysis . 20
Annex B: Determination of particle size distribution of mineral
soils by a hydrometer method following destruction
of organic matter. 23
Annex C: Bibliography. 30
© ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet central@iso.ch
X.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
ii
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ISO ISO 11277:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work of
preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 11277 was prepared by Technical Committee
ISO/TC 190, Soil quality, Subcommittee SC 5, Physical methods.
Annexes A and B form an integral part of this International Standard.
Annex C is for information only.
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Introduction
The physical and chemical behaviour of soils is controlled in part by the
amounts of mineral particles of different sizes in the soil. The subject of this
International Standard is the quantitative measurement of such amounts
(expressed as a proportion or percentage of the total mass of the mineral
soil), within stated size classes.
The determination of particle size distribution is affected by organic matter,
soluble salts, cementing agents (especially iron compounds), relatively
insoluble substances such as carbonates and sulfates, or combinations of
these. Some soils change their behaviour to such a degree upon drying,
that the particle size distribution of the dried material bears little or no
relation to that of the undried material encountered under natural
conditions. This is particularly true of soils rich in organic matter, those
developed from recent volcanic deposits, some highly weathered tropical
soils, and soils often described as “cohesive” [6]. Other soils, such as the
so-called "sub-plastic" soils of Australia, show little or no tendency to
disperse under normal laboratory treatments, despite field evidence of a
large clay content.
The procedures given in this International Standard recognize these kinds
of differences between soils from different environments, and the
methodology presented is designed to deal with them in a structured
manner. Such differences in soil behaviour can be very important, but
awareness of them depends usually on local knowledge. Given that the
laboratory is commonly distant from the site of the field operation, the
information supplied by field teams becomes crucial to the choice of an
appropriate laboratory procedure. This choice can be made only if the
laboratory is made fully aware of this background information.
All procedures in this International Standard should be carried out by
competent, trained persons, with adequate supervision. Attention is drawn
to certain known hazards, but it is essential that users follow safe working
practices. If in any doubt, seek professional advice.
It is essential that users of this International Standard read all of it
before commencing any operation, as failure to note certain points
will lead to incorrect analysis, and could be dangerous.
iv
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INTERNATIONAL STANDARD ISO ISO 11277:1998(E)
Soil quality — Determination of particle size distribution in mineral
soil material — Method by sieving and sedimentation
1 Scope
This International Standard specifies a basic method of determining particle size distribution applicable to a wide
range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to deal with
the less common soils mentioned in the introduction. This International Standard has been developed largely for
use in the field of environmental science, and its use in geotechnical investigations is something on which
professional advice might be required.
A major objective of this International Standard is the determination of enough size fractions to enable the
construction of a reliable particle size distribution curve.
This International Standard does not apply to the determination of the particle size distribution of the organic
components of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It should also
be realized that the chemical pretreatments and mechanical handling stages in this International Standard could
cause disintegration of weakly cohesive particles that, from field inspection, might be regarded as primary particles,
even though such primary particles could be better described as aggregates. If such disintegration is undesirable,
then this International Standard should not be used for the determination of the particle size distribution of such
weakly cohesive materials.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 565:1990, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings.
ISO 3310-1:1990, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth.
ISO 3310-2:1990, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal
plate.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
ISO 11464:1994, Soil quality — Pretreatment of samples for physico-chemical analyses.
©
ISO
3 Terminology and symbols
3.1 Terminology
Particles within particular size ranges or classes are commonly described as cobbles, gravel, coarse sand, silt, etc.
The meaning of such trivial names differs between countries, and in some cases there are no exact translations of
such words from one language to another; for example, the Dutch word "zavel" has no equivalent in English. The
only fraction for which there appears to be common agreement is clay, which is defined as material of less than
0,002 mm equivalent spherical diameter [1, 6]. Such trivial names shall not be used in describing the results of
particle size determination according to this International Standard. Phrases such as ".passing a 20 mm aperture
sieve." or ".less then 0,063 mm equivalent spherical diameter." shall be used instead. If trivial names must be
used, for example to cross-reference to another (inter-)national standard, then the trivial name should be defined
explicitly, so as to remove any doubt as to the meaning intended, e.g. silt (0,063 mm to 0,002 mm equivalent
spherical diameter) (clause 4 and, for example, [3]). Further, it is common to use the word 'texture' to describe the
results of particle size distribution measurements, e.g. 'the particle size of this soil is of clay texture'. This is incorrect
as the two concepts are different, and the word 'texture' shall not be used in the test report (clause 10) to describe
the results obtained by use of this International Standard.
It is common to refer to sieves as having a particular mesh-size or mesh number. These are not the same as the
sieve aperture, and the relationship between the various numbers is not immediately obvious. The use of mesh
numbers as a measurement of particle size is difficult to justify, and shall not be used in reporting the results of this
International Standard.
3.2 Symbols
The following symbols are found throughout the text and, where appropriate, units and quantities are as given below
(SI convention is followed for common units e.g. g = gram; m = metre; mm = millimetre; s = second, etc.).
Mg megagram (10 g)
mPa millipascal
t is the settling time, in seconds, of a particle of diameter d ;
p
η is the dynamic viscosity of water at the test temperature (see Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65; note in clause 4);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken as 1,00;
w
note in clause 4);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981);
d is the equivalent spherical diameter of the particle of interest, in millimetres;
p
4 Principle
Particle size distribution is determined by a combination of sieving and sedimentation, starting from air-dried soil [6]
(see note below). A method for undried soil is given in Annex A. Particles not passing a 2 mm aperture sieve are
determined by dry sieving. Particles passing such a sieve, but retained on a 0,063 mm aperture sieve, are
determined by a combination of wet and dry sieving, whilst particles passing the latter sieve are determined by
sedimentation. The pipette method is preferred. A hydrometer method is given in Annex B. A combination of sieving
and sedimentation enables construction of a continuous particle size distribution curve.
The key points in this procedure are summarized as a flow chart in Figure 2. This International Standard requires
that the proportions of fractions separated by sedimentation and sieving be determined from the masses of such
fractions obtained by weighing. Other methods of determining the mass of such fractions rely on such things as the
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interaction of particles with electromagnetic radiation or electrical fields [1]. There are often considerable difficulties
in relating the values obtained by different methods, one to another, for the same sample. It is one of the intentions
of this International Standard that close adherence to its details should help minimize interlaboratory variation in the
determination of the particle size distribution of mineral soils. Therefore the proportions of fractions shall be
determined only by weighing. If this is not the method used, then compliance with this International Standard cannot
be claimed in the test report (clause 10).
Both the pipette and hydrometer methods assume that the settling of particles in the sedimentation cylinder is in
accordance with Stokes' Law [1, 6, 9], and the constraints that this implies, namely:
a) the particles are rigid, smooth spheres;
b) the particles settle in laminar flow i.e. the Reynolds Number is less than about 0,2. This constraint sets an upper
equivalent spherical particle diameter (below) slightly greater than 0,06 mm for Stokesian settling under
gravity [1];
c) the suspension of particles is sufficiently dilute to ensure that no particle interferes with the settling of any other
particle;
d) there is no interaction between particle and fluid;
e) the diameter of the suspension column is large compared to the diameter of the particle, i.e. the fluid is of 'infinite
extent';
f) the particle has reached its terminal velocity;
g) the particles are of the same relative density.
Thus, the diameter of a particle is defined in terms of the diameter of a sphere whose behaviour in suspension
matches that of the particle. This is the concept of . It is the principle upon which the
equivalent spherical diameter
expression of the diameter of particles, as derived from sedimentation, is based in this International Standard.
Stokes' Law can be written, for the purposes of this International Standard, in the form:
t = 18ηh/[(ρ — ρ )gd ]
s w p
where
t is the settling time, in seconds, of a particle of diameter d (below);
p
η is the dynamic viscosity of water at the test temperature (Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65; see note);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken as 1,00;
w
see note);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981);
d is the equivalent spherical diameter of the particle of interest, in millimetres;
p
NOTE — It is realized that there are considerable differences between the densities of soil particles, but for the purposes of
this International Standard it is assumed that the mean particle density is that of quartz, i.e. 2,65 Mg/m [10], as this is the
3 3
commonest mineral in a very wide range of soils. The density of water is 0,9982 Mg/m and 0,9956 Mg/m at 20 °C and 30 °C,
respectively [8]. Given the effect of the addition of a small amount of dispersant (8.3.2), the density of water is taken as
1,0000 Mg/m over the permitted temperature range of this International Standard (8.2.2). Further, for routine use, it is
recommended that the sampling times be converted to minutes and/or hours, as appropriate, to lessen the risk of error
(Table 3).
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5 Field sampling
The mass of sample taken in the field shall be representative of the particle size distribution, especially if the
amount of the larger particles is to be determined reliably. Table 1 gives recommended minimum masses.
6 Sample preparation
Samples shall be prepared in accordance with the methods given in ISO 11464.
NOTE — For many purposes, particle size distribution is determined only for the fraction of the soil passing a 2 mm aperture
sieve. In this case, the test sample (8.5) may be taken either according to the procedures in ISO 11464 or from the material
passing a 2 mm aperture sieve according to 7.2.
7 Dry sieving (material > 2 mm)
7.1 General
The procedure specified in this clause applies to material retained on a 2 mm aperture sieve. Table 2 gives the
maximum mass which shall be retained on sieves of different diameters and apertures. If more than this amount of
material is retained, then it shall be subdivided appropriately, and resieved.
7.2 Apparatus
7.2.1 Test sieves, with apertures which comply with ISO 565, and with well-fitting covers and receivers.
The full range of sieves appropriate to the largest particle(s) present should be used (Table 1; note in 7.2.3). The
apertures chosen shall be stated in the test report (clause 10). The accuracy of the sieves shall be verified monthly
against a set of master sieves kept for this purpose, using an accepted method such as particle reference materials,
microscopy etc. [1] depending on the sieve aperture. Tolerances shall meet the requirements of ISO 3310-1 and
ISO 3310-2. Sieves that do not meet these specifications shall be discarded. A record shall be kept of such testing.
Brass sieves are particularly liable to splitting and distortion, and steel sieves are strongly recommended for the
larger apertures.
Special care shall be taken to ensure that covers and receivers do not leak. Sieves shall be inspected weekly when
in regular use, and on every occasion if used less often. A record shall be kept of such inspections. Round-hole
sieves shall not be used.
7.2.2 Balance, capable of weighing to an accuracy of within ± 0,5 g.
7.2.3 Mechanical sieve shaker
NOTE — It is usually impracticable to sieve mechanically at sieve apertures much greater than 20 mm, unless very heavy-
duty equipment is available. Mechanical sieve shaking is essential to sieve efficiency at smaller apertures.
7.2.4 A sieve brush and a stiff brush.
7.3 Procedure
Weigh the dry test sample, prepared in accordance with ISO 11464, to the nearest 0,5 g (m ). Place the weighed
material on the 20 mm sieve, and by brushing the material gently over the sieve apertures with the stiff brush (to
remove any adhering soil), sieve the material. Take care not to detach any fragments from the primary particles.
Sieve the retained material on the nest of sieves of selected apertures (7.1.1), and record the amount retained on
each sieve to the nearest 0,5 g. Do not overload the sieves (Table 1), but sieve the material in portions if necessary.
Weigh the material passing the 20 mm aperture sieve (m ), or a suitable portion of it (m ) (Table 2) obtained by an
2 3
appropriate subsampling method (clause 6), and place this on a nest of sieves, the lowermost having an aperture of
2 mm. Shake the sieves mechanically until no further material passes any of the sieves (see note). Record the
mass of material retained on each sieve and the mass passing the 2 mm aperture sieve.
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The total mass of the fractions should be within 1 % of m or m , as appropriate. If it is not, then check for sieve
2 3
damage, and discard sieves as appropriate (note in 7.2.3).
Sieve equipment performance should be verified against a suitable test material, e.g. standard particle reference
materials, ballotini, at intervals of one month. The results of this check shall be recorded.
NOTE — For practical purposes, it is usual to choose a standard sieve shaking time which gives an acceptable degree of
sieving efficiency with a wide range of soil materials. The minimum recommended period is 10 min.
Table 1 — Mass of soil sample to be taken for sieving
Maximum size of material forming >10% of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
63 50
50 35
37,5 15
28 6
20 2
14 1
10 0,5
6,3 0,5
5 0,2
2 or smaller 0,1
Table 2 — Maximum mass of material to be retained on each test sieve at the completion of sieving
Maximum mass
kg
Test sieve aperture Sieve diameter
mm
mm 450 300 200
50 10 4,5
37,5 8 3,5
28 6 2,5
20 4 2,0
14 3 1,5
10 2 1,0
6,3 1,5 0,75
5 1,0 0,5
3,35 0,3
2 0,2
1,18 0,1
0,6 0,075
0,425 0,075
0,3 0,05
0,212 0,05
0,15 0,04
0,063 0,025
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7.4 Calculation and expression of results
For the material retained by the 20 mm and larger aperture sieves, calculate the proportion by mass retained by
each sieve as a proportion of m . For example:
proportion retained on the 20 mm sieve = [m(20 mm)]/m
For the material passing the 20 mm sieve, multiply the mass of material passing each sieve by , and calculate
m /m
2 3
this as a proportion of m . For example:
proportion retained on the 6,3 mm sieve = m(6,3 mm)[(m /m )/m ]
2 3 1
Present the results as a table showing, to two significant figures, the proportion by mass retained on each sieve,
and the proportion passing the 2 mm sieve. The data shall also be used to construct a cumulative distribution curve
(Figure 1).
8 Wet sieving and sedimentation (material < 2 mm)
8.1 General
This clause specifies the procedure (see figure 2) for the determination of the particle size distribution of the
material passing the 2 mm aperture sieve down to <0,002 mm equivalent spherical diameter (see note). In order to
ensure that primary particles are measured rather than loosely bonded aggregates, organic matter and salts are
removed, especially sparingly soluble salts such as gypsum which would otherwise prevent dispersion and/or
promote flocculation of the finer soil particles in suspension (8.6), and a dispersing agent is added (8.8). These
procedures are required in this International Standard, and their omission shall invalidate its application. Sometimes
iron oxides, and carbonates, especially of calcium and/or magnesium, are also removed. Preferred procedures for
the removal of these compounds are given in the note in 8.7. The removal of any compound shall be recorded in the
test report (clause 10).
NOTE — Gravitational sedimentation can give a value for the total amount of material <0,002 mm equivalent spherical
diameter. However, the method cannot be used to divide this class further with reliability, as particles less than about 0,001 mm
equivalent spherical diameter can be kept in suspension almost indefinitely by Brownian motion [1].
8.2 Apparatus
The apparatus specified hereafter is sufficient to deal with one sample. Clearly it is more efficient to work in batches.
Experience has shown [9] that one operator can process up to 36 samples in a batch at a time given sufficient
apparatus and space, especially if calculations are dealt with by a computer.
8.2.1 Sampling pipette of a pattern similar to that in Figure 3 [4], the chief requirement being that the smallest
practicable zone of sedimenting suspension shall be sampled. The pipette shall be of not less than 10 ml volume
and shall be held in a frame so that it can be lowered to a fixed depth within a sedimentation tube (Figure 4).
NOTE — Experience suggests that a pipette with an upper volume of 50 ml is more than sufficient for most purposes. A 25 ml
volume pipette is a convenient compromise for routine analysis, but a smaller volume pipette will be found sufficient for soils
with down to about 10 % mass fraction <0,063 mm equivalent spherical diameter. Below this amount, greater precision is likely
to be obtained with a larger volume pipette.
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Figure 1 — Particle size distribution chart
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Figure 2 — Flow chart
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Dimensions in millimetres
1 Bulb capacity 125 ml approx.
2 Pipette and changeover cock capacity ~ 10 ml.
NOTE — This design has been found satisfactory, but alternative designs may be used.
Figure 3 — Sampling pipette for sedimentation test
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A and B 125 ml bulb funnel with stopcock G Sampling pipette
C Safety bulb suction inlet tube H Sedimentation tube
D Safety bulb D, F and G are joined to three-way stopcock E
F Outlet tube
1 Scale graduated in millimetres 3 Sliding panel
2 Clamps 4 Constant-temperature bath
NOTE — This design has been found satisfactory, but alternative designs may be used.
Figure 4 — Arrangement for lowering sampling pipette into soil suspension
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8.2.2 Constant temperature room or bath, which can be maintained at between 20 °C and 30 °C ± 0,5 °C. If a
bath is used, it shall accept a sedimentation tube immersed to the 500 ml mark, and shall not vibrate the contents of
the tube. Similarly, if a room is used, it, and its furniture, shall be constructed so that activity does not cause the
tubes and their contents to vibrate.
NOTE — This temperature range has been chosen to allow for the difficulties of maintaining one specified temperature in
different parts of the world. In addition, the lower temperature gives sedimentation times that fit well into an average working
day, whilst the upper temperature still allows for a sensible settling time for the fraction 0,063 mm equivalent spherical diameter
(clause 4, Table 3).
Table 3 — Pipette sampling times and d (for a particle density of 2,65 Mg/m )
p
at a sampling depth of 100 mm ± 1 mm at different temperatures
Times, after mixing, of starting sampling operation
st 1) nd rd st
Temperature 1 sample 2 sample 3 sample 4 sample
°C min s min s min s h min s
20 0 56 4 38 51 35 7 44 16
21 0 54 4 32 50 27 7 34 4
22 0 53 4 26 49 19 7 23 53
23 0 52 4 19 48 8 7 13 13
24 0 51 4 13 47 0732
25 049 4 745 52 6 52 50
26 0 48 4 2 44 536442
27 0 47 3 57 43 58 6 35 42
28 0 46 3 52 42 59 6 26 53
29 0 45 3 47 42 3 6 18 33
30 0 44 3 41 41 5 6 9 45
d (mm) 0,063 0,020 0,006 0,002
p
1) Sampling depth 200 mm ± 1 mm to allow adequate time for the stabilization of the suspension after mixing.
8.2.3 Two glass sedimentation tubes, without pouring lips, of approximate internal diameter 50 mm, and overall
length 350 mm, graduated at 500 ml volume, and with either rubber bungs to fit, or a stirrer.
8.2.4 Stirrer of noncorrodible material, as in Figure 5.
8.2.5 Five glass weighing vessels, with masses known to the nearest 0,000 1 g.
8.2.6 Mechanical shaker capable of keeping 30 g of soil in suspension in 150 ml of liquid. A device which rotates
the container end-over-end at 30 revolutions/min to 60 revolutions/min is suitable. The vigorous end-to-end type of
shaker, and the horizontal rotary shaker are both unsuitable, and neither shall be used (see note in 8.9).
8.2.7 Test sieves complying with ISO 565, ISO 3310-1 and ISO 3310-2, having apertures of 2 mm and 0,063 mm,
plus two intermediate sieves. The test report shall state which apertures are used. Round-hole sieves shall not be
used.
NOTE — The choice of the sieve of aperture 0,063 mm given here is for illustration, but accords with the widespread use of
this particle size to define the upper boundary of the silt fraction. Local requirements may decide on another aperture. The
choice of apertures for the intermediate sieves is a matter for local knowledge, but experience suggests that sieves of aperture
close to 0,2 mm and 0,1 mm are useful for a very wide range of soils.
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Dimensions in millimetres
Prepare a stirrer as shown, suitable materials being
a) brass or aluminium,
b) Perspex/Plexiglas
c) a section of a rubber stopper fitted onto a glass rod, etc.
Figure 5 — Stirrer; perforated stopper fitted onto glass rod, for example
8.2.8 Suitable sample divider (clause 6).
8.2.9 Balance, capable of weighing to an accuracy of within ± 0,000 1 g.
capable of maintaining a temperature between 105 °C and 110 °C.
8.2.10 Drying oven,
8.2.11 Stop clock, readable to 1 s.
8.2.12 Desiccator containing anhydrous silica gel (preferably of the self-indicating type), capable of holding the
five weighing vessels. The desiccant shall be inspected daily and dried at between 105 °C and 110 °C when no
longer effective.
8.2.13 A 650 ml tall-form glass beaker with cover glass to fit, or a 300 ml centrifuge bottle with a leakproof cap.
NOTE — This apparatus is used for chemical pretreatment, a constant problem during which is the adhesion of very fine
particles to glass. The problem is much reduced if the treatment is carried out in a polycarbonate or polysulfone centrifuge
bottle. Both materials will withstand repeated heating to 120 °C and are resistant to hydrogen peroxide and common dispersing
agents. Their use can also save significant amounts of operator time.
8.2.14 Centrifuge, capable of holding the 300 ml centrifuge bottles (see 8.8).
8.2.15 100 ml measuring cylinder.
8.2.16 25 ml pipette.
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8.2.17 Glass filter funnel capable of holding the 0,063 mm sieve.
8.2.18 Wash bottle containing water (8.3).
8.2.19 Rod, of glass or strong plastic, 150 mm to 200 mm long and at least 4 mm in diameter, with a rubber sleeve
at one end.
8.2.20 Electric hotplate, capable of maintaining a temperature between 105 °C and 110 °C.
NOTE — A hotplate is essential if polymer centrifuge bottles are used for the chemical pretreatment, but Bunsen, gauze and
tripod are sufficient if glass beakers are used.
8.2.21 Suction device similar to that shown in Figure 6 is useful, but not essential.
1 To vacuum 3 Pasteur pipette or similar
2 Flexible tube 4 Reservoir (5 l or 10 l)
Figure 6 — Sketch of suction device
8.2.22 Sieve brush.
8.2.23 Electrical conductivity meter accurate to 0,1 dS/m.
8.3 Reagents
All reagents shall be of recognized analytical grade. Use water conforming to class 2 of ISO 3696, i.e. having an
electrical conductivity no greater than 0,1 dS/m at 25 °C at the time of use.
8.3.1 Hydrogen peroxide solution, 30 % volume fraction.
NOTE — A 30 % volume fraction solution is one which will yield 30 ml of gaseous oxygen from 100 ml of solution (under
standard conditions of temperature and pressure) upon reduction to water either by chemical means, or by boiling.
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8.3.2 Solution of a dispersing agent.
The most widely used is that prepared by dissolving 33 g of sodium hexametaphosphate and 7 g of anhydrous
sodium carbonate in water to make 1 l of solution. This is the preferred dispersant. Store away from strong sunlight,
and preferably in a dark bottle. Record the date of preparation on the bottle. The solution is unstable and shall be
replaced after one month.
Buffered sodium hexametaphosphate is commonly referred to in the literature as "Calgon". This is a trade name.
The substance sold as such is often not the reagent described in this subclause, is of variable composition, and
shall not be used as a dispersing agent in the method given in this International Standard [11].
It is permissible to use other dispersing agents (see note), the choice of which shall be recorded in the test report
(clause 10). Whichever dispersant proves to be the most suitable for a particular soil, it is essential that the
suspension is examined visually to ensure that effective dispersion has occurred and that the dispersed suspension
is stable, i.e. that no flocculation has, or is, occurring. This inspection shall be carried out for each and every
sample.
NOTE — The sodium carbonate buffers the solution, and the suspension of the soil, to about pH 9,8. This dispersing agent
has been found successful with a very wide range of soils. However, if there are signs that dispersion is ineffective, consider
firstly that flocculating salts might be present (see 8.8). If dispersion is still unsuccessful after removal of salts, then other
dispersing agents should be considered. A very effective, but less widely used dispersing agent, is prepared by replacing the
sodium carbonate with 20 % volume fraction ammonia solution, in the ratio of 5 ml ammonia solution to 150 ml of the
hexametaphosphate solution. There are many other dispersing agents [2]. Whichever is chosen, considerable investigation will
be required to establish its effectiveness. It should be remembered that some soils show fewer problems of dispersion if
analysed without drying (Annex A). Some soils derived from recent volcanic deposits will disperse more effectively in an acid
medium [12].
8.3.3 Octan-2-ol or a similar volatile antifoaming agent.
NOTE — Octan-2-ol is highly effective and relatively long-lasting. Ethanol or methanol can also be used, but the use of
pentan-2-ol (amyl alcohol) is discouraged because it is potentially addictive.
8.4 Calibrations
8.4.1 Sampling pipette (Figure 4)
Clean and dry the pipette thoroughly and immerse the tip in water held at the same temperature as that of the
constant-temperature environment (8.2.2). By means of a tube attached to C, draw water into the pipette above E.
Drain off the water above E through F. Drain the pipette into a weighing bottle of known mass, and determine the
new mass. From the known masses calculate the internal volume of the pipette. Repeat this exercise three times
and take the average of the three volumes as the internal volume of the pipette to the nearest 0,05 ml (V ml).
c
8.4.2 Dispersing agent correction
Follow this procedure each time a new batch of dispersing agent is prepared.
Pipette 25 ml of dispersing agent solution into one of the glass sedimentation tubes, and fill the tube to the 500 ml
mark with water. Mix the contents of the tube thoroughly. Place the tube in the constant temperature environment,
and leave the tube for at least 1 h. Between any of the times at which samples may be taken from the sampling tube
(Table 3), take a sample (V ml) of the dispersing agent solution from the sedimentation tube using the sampling
c
pipette. Drain the pipette into a weighing vessel of known mass, and dry the contents of the vessel between 105 °C
and 110 °C. Allow the vessel to cool in the desiccator and determine the mass of the residue in the vessel to
0,000 1 g (m ).
r
NOTE — The minimum temperature equilibration period in the water bath is 1 h, but if a large number of tubes is placed in a
bath equilibration will take at least 4 h. In such cases it is advantageous to arrange the work so that equilibration takes place
overnight. Equilibration will be quicker if the supply of water used to fill up the tubes is kept at, or near to, the same temperature
as the constant-temperature environment.
8.5 The test sample
The test sample shall be taken from the material passing a 2 mm aperture sieve (clause 6 and 7.2) and weighed to
the nearest 0,001 g (m ). The mass of test sample depends on the type of soil. Approximately 30 g for a sandy soil
s
and 10 g for a clay soil are appropriate for pipette analysis, with proportionate masses for soils intermediate to these
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extremes. For the hydrometer method (Annex B), take twice this amount of material. Place the test sample in either
the 650 ml glass beaker or the 300 ml centrifuge bottle (8.2.13 and its note).
NOTE — Highly organic soils contain relatively little mineral matter. It might be necessary to take up to 100 g of such soils in
order to obtain sufficient mineral matter for a reliable analysis of the particle size distribution of this component. Such a large
amount of organic material should be apportioned between several vessels for ease of operation, with combination of the
mineral residues at a later stage.
8.6 Destruction of organic matter
Destroy the organic matter with hydrogen peroxide solution as follows. Add approximately 30 ml of water to the test
sample and allow it to become thoroughly wet (see note 1 below). Add 30 ml of 30 % volume fraction hydrogen
peroxide solution, and mix the contents of the vessel very gently using the glass or plastic rod. A vigorous reaction
can cause foaming of the sample mixture. This can be controlled by adding a few millilitres of octan-2-ol. Allow any
vigorous reaction to subside.
WARNING — Carry out this step with caution. Hydrogen peroxide can decompose violently with some
forms of organic matter, manganese compounds and finely-particulate iron sulfides, all of which can occur
in soil. Do not examine the reaction by looking into the top of the vessel, Do not accelerate an apparently
slow reaction by heating or addition of more hydrogen peroxide.
If using the 650 ml beaker, cover with the cover glass and leave overnight. Place the vessel on the hotplate or
bunsen burner, as appropriate (8.2.20) and warm gently. Control any foaming with octan-2-ol as before, and stir the
contents frequently. Do not allow the contents to dry out, adding more water if necessary. Bring the suspension to a
gentle boil and heat until all signs of bubbling due to decomposition of hydrogen peroxide have ceased. If there is
still undecomposed organic matter, remove the vessel from the heat, allow it to cool and repeat the treatment with
hydrogen peroxide. Highly organic soils will need several such treatments, the products of the reaction being
removed after every 2 or 3 treatments before continuing with more peroxide.
If destruction of organic matter has been carried out in a centrifuge bottle, bring the volume of the contents to
between 150 ml and 200 ml by addition of water. If a glass beaker has been used, then transfer the contents to a
centrifuge bottle, taking care to remove all traces of material from the sides of the beaker by means of the rubber
sleeve on the glass or plastic rod. Again, the final volume should be 150 ml to 200 ml. Centrifuge the bottle so as to
obtain a clear supernatant [15 min at a minimum relative centrifugal force (RCF) of 400g is recommended], and
decant the latter or remove by means of the suction device. Repeat the treatment until the supernatant is colourless
or nearly so.
NOTE 1 Dry organic materials are often strongly hydrophobic, in which case the addition of a few drops of octan-2-ol can be
beneficial.
If a centrifuge is not available, the mineral residues may be flocculated by adding 25 ml of 1 mol/l calcium chloride
solution. Stir thoroughly, bring to about 250 ml with water, allow to stand until the supernatant is clear, then siphon
or decant this from the residue. Add another 250 ml of water and repeat the washing procedure until the dark
residues of the decomposed organic matter have gone. Check that the electrical conductivity of the washings is
below 0,4 dS/m before attempting to disperse the residue (8.8).
Another alternative is to filter the residue from the oxidation step on a hardened, high wet-strength filter paper
(2,7 μm pore size is suitable), followed by thorough washing with water by means of the wash-bottle. It is essential
to observe the filtrate closely to see that no soil is lost. If particles pass through the filter paper, return the filtrate to
the container, add calcium chloride solution to the suspension as above, stir and refilter.
If flocculation with calcium chloride, or filtration are ineffective in preventing loss of fine soil particles, then a few
drops of a 60 g/l aluminium sulfate solution can be stirred into the soil suspension. The absolute minimum of
aluminium sulfate shall be used, as excess could cause problems in the subsequent dispersion of the soil.
NOTE 2 Lignified (woody) residues of plants are extremely difficult to decompose, and their complete destruction is often
impossible. Such fragments are usually regarded as decomposed when they have lost all traces of dark colour.
Transfer the washed residue quantitatively to a centrifuge bottle. In all cases, it is not essential for the supernatant
to be absolutely colourless, so long as it is obvious that the bulk of the dark decomposition products of the organic
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matter have been removed, but the solution shall be clear. The use of calcium chloride solution or aluminium sulfate
solution, in conjunction with filtration, decantation, suction or siphoning, shall be recorded on the test report
(clause 10).
8.7 Removal of soluble salts and gypsum
After removal of the residues following the destruction of organic matter, add sufficient water to the soil in the
centrifuge bottle so that the soil:water ratio is between 1:4 and 1:6 by volume. Shake the contents of the bottle
vigorously so that all the sediment is in suspension; then shake for 1 h on the end-over-end shaking machine.
Centrifuge to obtain a clear supernatant and measure its electrical conductivity (E ). If the latter is < 0,4 dS/m,
c
soluble salts and gypsum are not present in significant amounts. If the value of the E is > 0,4 dS/m, then remove
c
the supernatant in which the E was measured. Add 250 ml of water to the soil residue, cap the bottle and shake on
c
the end-over-end shaking machine for 1 h. Centrifuge to obtain a clear supernatant and measure the E again. If it
c
is < 0,4 dS/m, soluble salts and gypsum have been removed to an extent sufficient not to interfere in the dispersion
(8.8). If the E is > 0,4 dS/m, repeat the washing procedure until the E of the supernatant is < 0,4 dS/m. Record the
c c
removal of gypsum in the test report (clause 10).
Whilst the removal of soluble salts and gypsum is obligatory, that of iron (and associated aluminium) oxides, and of
carbonates is not (see note below). The removal of these compounds is a matter for local decision, but if done, the
preferred procedures are as follows. Iron oxides are removed by shaking the soil overnight with 40 g/l sodium
dithionite in ca. 0,3 mol/l sodium acetate solution buffered to pH 3,8 with acetic acid, in the ratio of 1 part soil to 40
parts of solution, both by volume.
Very iron-rich soils usually need several treatments. Magnetite is not affected by this procedure [7]. In certain soils,
especially those developed from recent volcanic deposits, this reagent can remove large quantities of aluminium as
well as iron. Calcium and magnesium carbonates are removed by treating the soil with the minimum possible
excess of aqueous hydrochloric acid.
The following procedure has been found to be applicable to a wide range of soils, and is best applied to the soil after
the removal of organic matter (8.6). Where the carbonate content is greater than about 2 % mass fraction, add to
the washed, centrifuged soil (above) 4 ml of 1 mol/l hydrochloric acid for each percent of carbonate, plus an excess
of 25 ml of acid. Make up to about 250 ml with water, and place the suspension on the water bath at about 80 °C for
15 min, stirring the suspension from time to time. Remove from the water bath and leave the suspension to stand
overnight. If the soil flocculates sufficiently to lea
...
NORME ISO
INTERNATIONALE 11277
Première édition
1998-05-15
Qualité du sol — Détermination de la
répartition granulométrique de la matière
minérale des sols — Méthode par tamisage
et sédimentation
Soil quality — Determination of particle size distribution in mineral soil
material — Method by sieving and sedimentation
A
Numéro de référence
Sommaire Page
1 Domaine d'application. 1
2 Références normatives. 1
3 Terminologie, symboles et unités . 2
4 Principe. 3
5 Échantillonnage sur le terrain . 4
6 Préparation des échantillons . 4
7 Tamisage à sec (matériau . 2 mm). 4
8 Tamisage humide et sédimentation (matériau , 2 mm) . 6
9 Fidélité . 19
10 Rapport d'essai. 20
Annexe A (normative) Détermination de la distribution
granulométrique de la fraction minérale des sols non séchés
avant analyse. 21
Annexe B (normative) Détermination de la distribution
granulométrique de la fraction minérale des sols par la méthode
du densimètre après destruction de la matière organique. 24
Annexe C (informative) Bibliographie. 32
© ISO 1998
Droits de reproduction réservés. Sauf prescription différente, aucune partie de cette publi-
cation ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun pro-
cédé, électronique ou mécanique, y compris la photocopie et les microfilms, sans l'accord
écrit de l'éditeur.
Organisation internationale de normalisation
Case postale 56 • CH-1211 Genève 20 • Suisse
Internet iso@iso.ch
Imprimé en Suisse
ii
©
ISO ISO 11277:1998(F)
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération
mondiale d'organismes nationaux de normalisation (comités membres de
l'ISO). L'élaboration des Normes internationales est en général confiée aux
comités techniques de l'ISO. Chaque comité membre intéressé par une
étude a le droit de faire partie du comité technique créé à cet effet. Les
organisations internationales, gouvernementales et non gouvernementales,
en liaison avec l'ISO participent également aux travaux. L'ISO collabore
étroitement avec la Commission électrotechnique internationale (CEI) en
ce qui concerne la normalisation électrotechnique.
Les projets de Normes internationales adoptés par les comités techniques
sont soumis aux comités membres pour vote. Leur publication comme
Normes internationales requiert l'approbation de 75 % au moins des
comités membres votants.
La Norme internationale ISO 11277 a été élaborée par le comité technique
ISO/TC 190, Qualité du sol, sous-comité SC 5, Méthodes physiques.
Les annexes A et B font partie intégrante de la présente Norme
internationale. L’annexe C est donnée uniquement à titre d'information.
iii
©
Introduction
Le comportement physique et chimique des sols est contrôlé en partie par
les quantités de particules minérales de différentes tailles qui s’y trouvent.
L’objet de la présente Norme internationale est la mesure de ces quantités
(exprimée en proportion ou en pourcentage de la masse totale du sol
minéral), au sein de classes de tailles indiquées.
La détermination de la distribution granulométrique est affectée par la
matière organique, les sels solubles, les agents de cémentation (particu-
lièrement les oxydes de fer), les substances relativement insolubles
comme les carbonates et les sulfates, ou les combinaisons de ceux-ci. Le
comportement de certains sols change dans une telle proportion au
séchage que la distribution granulométrique de la matière sèche a peu ou
pas de rapport avec celle de la matière que l'on trouve dans des conditions
naturelles. Ceci est particulièrement vrai pour les sols riches en matière
organique, ceux élaborés à partir de dépôts volcaniques récents, certains
sols tropicaux altérés et les sols souvent décrits comme «à forte cohé-
sion» [6]. D'autres sols, comme les sols nommés «sub-plastic» d'Australie,
montrent peu ou pas de tendance à se disperser dans le cadre de
traitements normaux de laboratoire, en dépit d'une importante teneur en
argile mise en évidence sur le terrain.
Les modes opératoires indiqués dans la présente Norme internationale
tiennent compte des différences entre les sols provenant d'environnements
différents, et la méthodologie présentée est conçue pour les traiter de
façon structurée. Ces différences de comportement du sol peuvent être
très importantes, mais leur perception dépend généralement de la
connaissance locale. Étant donné que le laboratoire est souvent éloigné du
site de prélèvement sur le terrain, les informations fournies par l'équipe sur
le terrain deviennent cruciales pour le choix d'un mode opératoire
approprié de laboratoire. Ce choix ne peut être fait que si le laboratoire est
pleinement informé de ces données de base.
Il convient que les modes opératoires de la présente Norme internationale
soient tous mis en œuvre par du personnel compétent, formé et
convenablement encadré. L'attention est attirée sur certains phénomènes
dangereux connus, mais il est néanmoins essentiel que les utilisateurs
respectent les consignes de sécurité dans leurs pratiques de travail et,
qu'en cas de doute, ils recherchent un avis compétent.
Il est également essentiel que les utilisateurs de la présente Norme
internationale la lisent en entier avant d'entamer une opération
quelconque, tout défaut de lecture de certains points pouvant
entraîner des erreurs d'analyse et donc des dangers.
iv
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NORME INTERNATIONALE ISO ISO 11277:1998(F)
Qualité du sol — Détermination de la répartition granulométrique
de la matière minérale des sols — Méthode par tamisage et
sédimentation
1 Domaine d'application
La présente Norme internationale spécifie une méthode de base de détermination de la distribution granulométrique
des matières minérales des sols, y compris la fraction minérale des sols organiques. Elle propose également des
procédures permettant de traiter les sols particuliers cités dans l'introduction. La présente Norme internationale a
été élaborée pour être largement utilisée dans le domaine de la science de l'environnement, et son utilisation dans
des recherches géotechniques est un point pour lequel un avis professionnel peut se révéler nécessaire.
Un objectif majeur de la présente Norme internationale est la détermination d'un nombre suffisant de fractions
granulométriques pour permettre la construction d'une courbe de distribution granulométrique significative.
La présente Norme internationale ne s'applique pas à la détermination de la distribution granulométrique des
composants organiques du sol, à savoir les restes plus ou moins fragiles, partiellement décomposés, de plantes ou
d'animaux. Il convient également de savoir que les traitements chimiques préalables et les étapes de manipulation
mécanique dans la présente Norme internationale peuvent entraîner la désintégration de particules à faible
cohérence qui, du point de vue d'une inspection sur le terrain, pourraient être considérées comme des particules
primaires et mieux décrites en tant qu'agrégats. Si cette désintégration n'est pas souhaitable, il convient de ne pas
utiliser la présente Norme internationale pour la détermination de la distribution granulométrique de ces matières à
faible cohérence.
2 Références normatives
Les normes suivantes contiennent des dispositions qui, par suite de la référence qui en est faite, constituent des
dispositions valables pour la présente Norme internationale. Au moment de la publication, les éditions indiquées
étaient en vigueur. Toute norme est sujette à révision et les parties prenantes des accords fondés sur la présente
Norme internationale sont invitées à rechercher la possibilité d'appliquer les éditions les plus récentes des normes
indiquées ci-après. Les membres de la CEI et de l'ISO possèdent le registre des Normes internationales en vigueur
à un moment donné.
ISO 565:1990, Tamis de contrôle — Tissus métalliques, tôles métalliques perforées et feuilles électroformées —
Dimensions nominales des ouvertures.
ISO 3310-1:1990, Tamis de contrôle — Exigences techniques et vérifications — Partie 1: Tamis de contrôle en
tissus métalliques.
ISO 3310-2:1990, Tamis de contrôle — Exigences techniques et vérifications — Partie 2: Tamis de contrôle en
tôles métalliques perforées.
ISO 3696:1987, Eau pour laboratoire à usage analytique — Spécifications et méthodes d'essai.
ISO 11464:1994, Qualité du sol — Prétraitement des échantillons pour analyses physico-chimiques.
©
ISO
3 Terminologie, symboles et unités
3.1 Terminologie
Les particules appartenant à des gammes ou des classes de tailles particulières sont généralement décrites
comme des galets, des graviers, du sable grossier, des limons, etc. La signification de ces appellations consacrées
par l'usage diffère selon les pays et dans certains cas il n'existe pas de traduction exacte de ces mots d'une langue
à l'autre; par exemple, le mot néerlandais «zavel» n'a pas d'équivalent en anglais. La seule fraction pour laquelle il
semble y avoir un accord est l'argile qui est définie comme une matière de moins de 0,002 mm de diamètre
sphérique équivalent [1, 6]. Ces appellations traditionnelles ne doivent pas être utilisées pour décrire les résultats
de la détermination granulométrique conformément à la présente Norme internationale. Des phrases comme «.
traversant un tamis à ouverture de 20 mm .» ou «. inférieur à un diamètre sphérique équivalent de 0,063 mm.»
doivent être utilisées à la place. Si les appellations traditionnelles doivent être utilisées, par exemple en référence
croisée avec une autre norme (inter)nationale, le nom populaire doit être explicitement défini, de façon à éliminer
tout doute sur la signification voulue, par exemple limon (diamètre sphérique équivalent de 0,063 mm à 0,020 mm)
(voir l’article 4 et, par exemple, [3]). En outre, il est courant d'utiliser le mot «texture» pour décrire les résultats de
mesurage de distribution granulométrique, par exemple «la taille de particule de ce sol est une texture argileuse».
Ceci est incorrect car les deux concepts sont différents, et le mot «texture» ne doit pas être utilisé dans le rapport
d'essai (article 10) pour décrire les résultats obtenus en utilisant la présente Norme internationale.
Il est courant de dire que les tamis ont un «numéro de vide de maille» ou un «numéro de maille» particulier. Ces
termes ne sont pas équivalents du terme «ouverture» et les rapports entre les différents numéros ne sont pas
immédiatement évidents. Il est difficile de justifier l'utilisation des numéros de maille comme mesure de la taille de
particules et il ne faut donc pas les indiquer dans le rapport donnant les résultats de la présente Norme
internationale.
3.2 Symboles et unités
Les symboles qui suivent sont utilisés dans le texte; ils sont accompagnés, le cas échéant, des unités et grandeurs
correspondantes (les conventions du système international SI sont respectées pour les unités courantes, par
exemple g = gramme; m = mètre; mm = millimètre; s = seconde, etc.).
Mg mégagramme (10 g);
mPa millipascal;
t est le temps, en secondes, de décantation d'une particule de diamètre d ;
p
h est la viscosité dynamique de l'eau à la température d'essai (voir tableau B.2), en millipascals par
seconde;
h est la profondeur de prélèvement, en centimètres;
r est la masse volumique moyenne des particules, en mégagrammes par mètre cube (considérée égale à
s
2,65; voir note à l’article 4);
r est la masse volumique du liquide contenant la suspension de sol, en mégagrammes par mètre cube
w
(considérée égale à 1,00; voir note à l’article 4);
est l'accélération due à la pesanteur, en centimètres par seconde carrée (c'est-à-dire 981);
g
d est le diamètre sphérique équivalent de la particule concernée, en millimètres.
p
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ISO
4 Principe
La distribution granulométrique est déterminée par une combinaison de tamisage et de sédimentation à partir d'un
sol séché à l'air [6] (voir note ci-dessous). Une méthode pour un sol non séché est donnée à l’annexe A. Les
particules ne traversant pas un tamis à ouverture de 2 mm sont déterminées par tamisage à sec. Les particules
traversant un tel tamis, mais retenues sur un tamis à ouverture de 0,063 mm sont déterminées par une
combinaison de tamisage par voie humide et par voie sèche, alors que les particules traversant le dernier tamis
sont déterminées par sédimentation. Le prélèvement à la pipette constitue la méthode recommandée. Une méthode
par mesure de la masse volumique est donnée à l’annexe B. La combinaison du tamisage et de la sédimentation
permet l'élaboration d'une courbe continue de granulométrie.
Les points clés de ce mode opératoire sont résumés sous forme d'algorithme à la figure 2. La présente Norme
internationale exige que les proportions des fractions séparées par sédimentation et tamisage soient déterminées à
partir des masses obtenues par pesée. D'autres méthodes de détermination de la masse des fractions reposent sur
des principes tels que l'interaction des particules avec un rayonnement électromagnétique ou des champs
électriques [1]. Il est souvent extrêmement difficile de corréler les valeurs obtenues par ces différentes méthodes
pour un même échantillon. Un des buts visés par la présente Norme internationale est donc d'aider, par un respect
strict des détails indiqués, à minimiser la variation de la distribution granulométrique des sols minéraux déterminée
par différents laboratoires. Les proportions des différentes fractions ne doivent donc être déterminées que par
pesée. Aucune présomption de conformité ne pourra être revendiquée dans le rapport d'essai (article 10) si cette
méthode n'est pas utilisée.
Les méthodes de la pipette et du densimètre supposent que la décantation des particules dans le cylindre de
sédimentation est conforme à la loi de Stokes [1, 6, 9] avec les contraintes que cela implique, à savoir:
a) les particules sont des sphères lisses et rigides;
b) la décantation des particules s'effectue en écoulement laminaire, c'est-à-dire un écoulement dont le nombre de
Reynolds est inférieur à 0,2. Cette contrainte fixe un diamètre sphérique équivalent maximal de particule
légèrement supérieur à 0,06 mm pour que la décantation se fasse par gravité selon la loi de Stokes [1];
c) la suspension des particules est suffisamment diluée pour garantir qu'aucune particule n'affecte la décantation
d'autres particules;
d) il n'y a pas d'interaction entre la particule et le fluide;
e) le diamètre de la colonne de suspension est grand par rapport au diamètre de la particule, c'est-à-dire que le
fluide est à «étendue infinie»;
f) la particule atteint sa vitesse limite;
g) les particules ont la même densité.
Ainsi, le diamètre d'une particule est défini en termes de diamètre d'une sphère dont le comportement en
suspension correspond à celui de la particule. Ceci correspond au concept de diamètre sphérique équivalent. C'est
le principe sur lequel se fonde dans la présente Norme internationale l'expression du diamètre des particules
dérivant de la sédimentation.
La loi de Stokes peut, pour les besoins de la présente Norme internationale, être écrite sous la forme suivante:
th=18hr-rgd
()
sw p
où
t est le temps, en secondes, de décantation d'une particule de diamètre d (voir ci-dessous);
p
h est la viscosité dynamique de l'eau à la température d'essai (voir tableau B.2), en millipascals par
seconde;
h est la profondeur de prélèvement, en centimètres;
r est la masse volumique moyenne des particules, en mégagrammes par mètre cube (considérée égale à
s
2,65, voir note);
©
ISO
r est la masse volumique du liquide contenant la suspension de sol, en mégagrammes par mètre cube
w
(considérée égale à 1,00, voir note);
g est l'accélération due à la pesanteur, en centimètres par seconde carrée (c'est-à-dire 981);
d est le diamètre sphérique équivalent de la particule concernée, en millimètres.
p
NOTE Il est reconnu qu'il existe des différences considérables entre les masses volumiques des particules du sol, mais dans
le cadre de la présente Norme internationale, il est supposé que la masse volumique moyenne des particules est celle du
quartz, c'est-à-dire 2,65 Mg/m [10], car c'est le minéral le plus commun dans une très large gamme de sols. La masse
3 3
volumique de l'eau est de 0,998 2 Mg/m et de 0,995 6 Mg/m à 20 °C et 30 °C respectivement [8]. Étant donné l'effet de l'ajout
d'une petite quantité de dispersant (8.3.2.), la masse volumique de l'eau est prise égale à 1,000 0 Mg/m pour la gamme de
température autorisée de la présente Norme internationale (8.2.2). En outre, pour l'usage courant, il est recommandé que les
temps d'échantillonnage soient convertis en minutes et/ou heures, de manière appropriée, afin de réduire le risque d'erreur
(voir tableau 3).
5 Échantillonnage sur le terrain
La masse d'échantillon prélevée sur le terrain doit être représentative de la distribution granulométrique,
particulièrement si la quantité des particules les plus volumineuses doit être déterminée de façon fiable. Le
tableau 1 donne les masses minimales recommandées.
6 Préparation des échantillons
Les échantillons doivent être préparés conformément aux méthodes données dans l'ISO 11464.
NOTE Pour de nombreuses applications, la distribution granulométrique n'est déterminée que pour la fraction de sol
traversant un tamis de 2 mm d'ouverture de mailles. Dans ce cas, la prise d'essai (8.5) peut être prélevée conformément aux
modes opératoires de l'ISO 11464 ou bien à partir de la matière traversant un tamis de 2 mm d'ouverture de mailles
conformément à 7.3.
7 Tamisage à sec (matériau . 2 mm)
7.1 Généralités
Le mode opératoire spécifié dans le présent article s'applique à la matière retenue sur un tamis de 2 mm
d'ouverture de mailles. Le tableau 2 donne la masse maximale qui doit être retenue sur des tamis de différents
diamètres et de différentes ouvertures. Si la quantité de matériau retenue est supérieure, elle doit être subdivisée
de façon appropriée et retamisée.
7.2 Appareillage
7.2.1 Tamis de contrôle, conformes à l'ISO 565, avec des couvercles et des réceptacles appropriés.
Il est recommandé d'utiliser toute la gamme des tamis correspondant à la taille maximale de particules présentes
(tableau 1, note en 7.2.3). Les ouvertures choisies doivent être indiquées dans le rapport d'essai (article 10). La
précision des tamis doit être contrôlée mensuellement par rapport à un jeu de tamis étalons conservés à cet effet et
à l'aide d'une méthode reconnue, comme par exemple la comparaison avec des matériaux de référence, l'analyse
au microscope, etc. en fonction de l'ouverture du tamis [1]. Les tolérances doivent respecter les prescriptions de
l’ISO 3310-1 et de l’ISO 3310-2. Les tamis ne respectant pas ces prescriptions doivent être mis au rebut. Un
enregistrement des résultats d'essai doit être conservé.
Les tamis en laiton sont particulièrement sujets aux détériorations et aux déformations. Les tamis en acier sont
vivement recommandés pour les ouvertures importantes.
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ISO
Il convient de s'assurer que les couvercles et réceptacles ne fuient pas. Les tamis doivent être inspectés chaque
semaine lorsqu'ils sont utilisés régulièrement, et à chaque utilisation s'ils sont sollicités moins souvent. Un
enregistrement de ces inspections doit être conservé. Les tamis à trous ronds ne doivent pas être utilisés.
7.2.2 Balance, précise à – 0,5 g près.
7.2.3 Tamiseur mécanique.
NOTE Il est généralement peu pratique de tamiser mécaniquement à des ouvertures de tamis supérieures à 20 mm, sauf si
un équipement à haute capacité est disponible. Le tamiseur de tamis mécanique est essentiel pour tamiser efficacement à des
ouvertures plus petites.
7.2.4 Brosse pour tamis et brosse à poil dur.
7.3 Mode opératoire
Peser l'échantillon à tamiser, préparé selon les instructions de l'ISO 11464, à 0,5 g près (m ). Placer le matériau
pesé sur le tamis de 20 mm et, en brossant doucement la matière au-dessus des mailles du tamis avec la brosse à
poil dur (pour retirer la terre qui adhère), tamiser l'échantillon. Veiller à ne pas détacher de fragments des particules
primaires. Tamiser le refus sur une colonne de tamis d'ouvertures choisies (voir 7.2.1), et enregistrer la quantité
retenue sur chaque tamis à 0,5 g près. Ne pas surcharger les tamis (voir tableau 1), mais tamiser par portions, si
nécessaire.
Peser la matière traversant le tamis à ouverture de 20 mm (m ), ou une partie convenable de celle-ci (m ) (voir
2 3
tableau 2) obtenue par une méthode appropriée de sous-échantillonnage (article 6), et la placer sur une colonne de
tamis dont le plus bas a une ouverture de 2 mm. Secouer les tamis avec un moyen mécanique jusqu'à ce
qu'aucune matière ne les traverse (voir note). Enregistrer la masse de matière retenue sur chaque tamis et la
masse traversant le tamis à ouverture de 2 mm.
La masse totale des fractions doit être égale, à moins de 1 % près, à m ou m selon la méthode utilisée. Si elle ne
2 3
l'est pas, vérifier si un tamis est endommagé et le changer si nécessaire (voir note en 7.2.3).
La performance de l'équipement doit être vérifiée tous les mois par rapport à un échantillon de contrôle approprié,
par exemple un échantillon de référence à valeurs certifiées. Les résultats de cette vérification doivent être
enregistrés.
NOTE Pour des raisons pratiques, il est courant de choisir une durée standard de tamisage qui donne un niveau acceptable
d'efficacité pour une large gamme d'échantillons. La durée minimale recommandée est de 10 min.
Tableau 1 — Masse d'échantillon de sol à prélever pour le tamisage
Dimension maximale des particules constituant plus Masse minimale d'échantillon à prélever
de 10 % du sol pour le tamisage
(donnée comme ouverture du tamis de contrôle, en mm) (donnée en kg)
63 50
50 35
37,5 15
28 6
20 2
14 1
10 0,5
6, 3 0,5
5 0,2
2 ou plus petit 0,1
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ISO
Tableau 2 — Masse maximale de matière pouvant être retenue sur chaque tamis de contrôle
à l'achèvement du tamisage
Masse maximale
kg
Dimension de l'ouverture
du tamis de contrôle
Diamètre du tamis
mm
mm 450 300 200
50 10 4,5
37,5 8 3,5
28 6 2,5
20 4 2,0
14 3 1,5
10 2 1,0
6,3 1,5 0,75
5 1,0 0,5
3,35 0,3
2 0,2
1,18 0,1
0,6 0,075
0,425 0,075
0,3 0,05
0,212 0,05
0,15 0,04
0,063 0,025
7.4 Calcul et expression des résultats
Pour les matériaux retenus par le tamis de 20 mm et le tamis ayant la plus grande ouverture, calculer la proportion
de masse retenue par chaque tamis par rapport à m . Par exemple:
proportion retenue sur le tamis de 20 mm = [m(20 mm)]/m
Pour les matériaux traversant le tamis de 20 mm, multiplier la masse de la matière traversant chaque tamis par
m /m et calculer par rapport à m . Par exemple:
2 3 1
proportion retenue sur le tamis de 6,3 mm = m(6,3 mm) × (m /m )/m
2 3 1
Présenter les résultats dans un tableau montrant, à deux chiffres significatifs, la proportion en masse retenue sur
chaque tamis, et la proportion traversant le tamis de 2 mm. Utiliser également ces données pour élaborer une
courbe de distribution cumulative (voir figure 1).
8 Tamisage humide et sédimentation (matériau , 2 mm)
8.1 Généralités
Le présent article décrit le mode opératoire (voir figure 2) pour la détermination de la distribution granulométrique de
la matière traversant le tamis à ouverture de 2 mm jusqu'à un diamètre sphérique équivalent 0,002 mm (voir
,
note). Afin de garantir que les particules primaires sont mesurées plutôt que des agrégats faiblement adhérents, la
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ISO
matière organique et les sels sont éliminés, particulièrement les sels peu solubles comme le gypse, qui
empêcheraient la dispersion et/ou entraîneraient la floculation des particules plus fines en suspension (8.7). Un
agent dispersant est ajouté (8.8). Ce sont des procédures obligatoires dans la présente Norme internationale et leur
omission peut invalider l'application de celle-ci. Parfois, des oxydes de fer et des carbonates, en particulier de
calcium et/ou de magnésium, sont également éliminés. Les modes opératoires recommandés pour l'élimination de
ces composés sont indiqués à la note en 8.7. L'élimination de tout composé doit être enregistrée dans le rapport
d'essai (article 10).
NOTE La sédimentation par gravité peut donner une valeur pour la quantité totale de matériaux ayant un diamètre sphérique
équivalent , 0,002 mm. Cependant, la méthode ne peut être utilisée pour diviser davantage cette classe avec fiabilité, car des
particules ayant un diamètre sphérique équivalent inférieur à environ 0,001 mm peuvent rester en suspension presque
indéfiniment à cause du mouvement brownien [1].
8.2 Appareillage
L'appareillage décrit ci-après est prévu pour traiter un seul échantillon. En fait, il est plus rentable de travailler avec
des lots d'échantillons. L'expérience a montré [9] qu'un opérateur peut traiter simultanément une série de
36 échantillons, avec un appareillage et un espace suffisants, en particulier si les calculs sont effectués par
ordinateur.
8.2.1 Pipette de prélèvement, d'un modèle similaire à celui de la figure 3 [4], la principale exigence étant que la
plus petite zone possible de suspension doit être prélevée. La pipette ne doit pas avoir un volume inférieur à 10 ml
et doit être tenue par un châssis afin de pouvoir être abaissée à une profondeur déterminée à l'intérieur du tube de
sédimentation (figure 4).
NOTE L'expérience montre qu'un volume maximal de 50 ml est plus que suffisant pour la plupart des objectifs. Une pipette
de 25 ml est un compromis convenable pour une analyse de routine mais une pipette de plus petit volume sera suffisante pour
des sols dont environ 10 % des fractions ont un diamètre sphérique équivalent , 0,063 mm. Au-dessous de cette quantité, une
précision supérieure peut être obtenue avec une pipette de plus grand volume.
Tableau 3 — Temps de prélèvement à la pipette et diamètres sphériques équivalents, d ,
p
(pour une masse volumique de particule de 2,65 Mg/m³) pour une profondeur de prélèvement
de 100 mm – 1 mm et à des températures différentes
Temps de démarrage de l'opération de prélèvement, après mélange
Tempé-
er 1) ème ème ème
1 prélèvement 2 prélèvement 3 prélèvement 4 prélèvement
rature
°C min s min s min s h min s
20 0 56 4 38 51 35 7 44 6
21 0 54 4 32 50 27 7 34 4
22 0 53 4 26 49 19 7 23 53
23 0 52 4 19 48 8 7 13 13
24 0 51 4 13 47 0 7 3 2
25 0 494 745 52652 50
26 0 484 244 53644 2
27 0 47 3 57 43 58 6 35 42
28 0 46 3 52 42 59 6 26 53
29 0 45 3 47 42 3 6 18 33
30 0 44 3 41 41 5 6 9 45
d (mm) 0,063 0,020 0,006 0,002
p
1) Profondeur de prélèvement portée à 200 mm – 1 mm pour disposer d'un temps suffisant de stabilisation de la suspension après
mélange.
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Figure 1 — Diagramme de distribution granulométrique
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Figure 2 — Diagramme du mode opératoire
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Dimensions en millimètres
1 Capacité de l'entonnoir cylindrique ~ 125 ml 2 Capacité de la pipette et du robinet ~ 10 ml
NOTE Ce montage donne de bons résultats mais d'autres conceptions peuvent également être utilisées.
Figure 3 — Pipette de prélèvement pour essai de sédimentation
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A et B Entonnoir cylindrique de 125 ml avec robinet d'arrêt G Pipette de prélèvement
C Tube d'aspiration de sureté H Tube de sédimentation
D Ampoule d'aspiration D, F et G sont reliés au robinet E à 3 voies
F Tube de sortie
1 Échelle graduée en millimètres 3 Panneau coulissant
2 Colliers 4 Bain thermostaté
NOTE Ce montage donne de bons résultats mais d'autres conceptions peuvent également être utilisées.
Figure 4 — Disposition pour une pipette de prélèvement s'abaissant dans la suspension de sol
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8.2.2 Pièce à température constante ou bain thermostaté, dans lesquels la température peut être maintenue
constante entre 20 °C et 30 °C – 0,5 °C. Si un bain est utilisé, il doit accepter un tube de sédimentation immergé
jusqu'au trait de jauge de 500 ml et ne doit pas faire vibrer le contenu du tube. De même, si une salle est utilisée,
elle et son mobilier doivent être construits de façon à éviter la vibration des tubes et de leur contenu.
NOTE Cet intervalle de température a été choisi pour tenir compte des difficultés à maintenir une température spécifiée dans
différentes parties du monde. En outre, la température inférieure donne des durées de sédimentation qui s'adaptent bien à une
journée de travail moyenne, alors que la température supérieure permet encore une durée de sédimentation correcte pour la
fraction de diamètre sphérique équivalent de 0,063 mm (voir article 4 et tableau 3).
8.2.3 Deux tubes de sédimentation en verre, sans bec verseur, d'un diamètre intérieur d'environ 50 mm, et
d'une longueur totale de 350 mm, gradués à un volume de 500 ml, avec des bouchons de caoutchouc adaptés, ou
bien (si l'on prévoit une agitation par retournement) un système de mise en supension.
, constitué d'un matériau inerte, tel que présenté à la figure 5.
8.2.4 Système de mise en suspension
Dimensions en millimètres
Préparer un système tel qu’illustré; des matériaux convenables sont, entre autres:
a) laiton ou aluminium c) section de bouchon en caoutchouc emmanché sur une tige en verre, etc.
b) Perspex/Plexiglas
Figure 5 — Système de mise en suspension — Bouclier perforé monté sur une tige en verre, par exemple
8.2.5 Cinq cristallisoirs en verre, de masse connue à 0,000 1 g près.
, pouvant maintenir 30 g de terre en suspension dans 150 ml de liquide. Un agitateur
8.2.6 Agitateur mécanique
rotatif par retournement de 30 r/min à 60 r/min convient. L'agitateur énergique en va-et-vient et l'agitateur rotatif
dans le plan horizontal ne conviennent pas et ne doivent jamais être utilisés (voir également note en 8.9).
8.2.7 Tamis de contrôle, conformes à l’ISO 565, l’ISO 3310-1 et l’ISO 3310-2, ayant des ouvertures de 2 mm et
de 0,063 mm, plus deux tamis intermédiaires. Le rapport d'essai doit indiquer les ouvertures utilisées. Les tamis à
trous ronds ne doivent pas être utilisés.
NOTE Le choix du tamis à ouverture de 0,063 mm donné ici sert d'illustration mais correspond à l'usage courant qui veut que
cette taille de particule définisse la limite supérieure de la fraction limon. Les exigences locales peuvent décider d'autres
ouvertures. Le choix des ouvertures des tamis intermédiaires est une question de connaissances locales mais l'expérience
suggère que des ouvertures voisines de 0,2 mm et 0,1 mm sont utiles pour toute une variété de sols.
8.2.8 Diviseur d'échantillons approprié (article 6).
8.2.9 Balance, précise à 0,000 1 g près.
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8.2.10 Étuve, pouvant maintenir une température comprise entre 105 °C et 110 °C.
8.2.11 Minuterie d'arrêt, précise à 1 s près.
8.2.12 Dessiccateur, contenant du gel de silice anhydre (de préférence indiquant son degré d'humidité), pouvant
contenir les cinq cristallisoirs de pesée. Le déshydratant doit être inspecté chaque jour et séché entre 105 °C et
110 °C lorsqu'il n'est plus efficace.
8.2.13 Bécher en verre, de forme haute de 650 ml avec verre de montre adapté à l'ouverture, ou flacon à
centrifuger de 300 ml muni d'un couvercle étanche.
NOTE Cet appareillage est utilisé pour le traitement chimique préalable. Au cours de celui-ci, un problème constant est
l'adhérence de très fines particules au verre. Le problème est très réduit si le traitement est effectué dans un flacon à
centrifuger en polycarbonate ou en polysulfone. Ces deux matériaux supportent un chauffage répété à 120 °C et résistent au
peroxyde d'hydrogène et aux agents dispersants communs. Leur utilisation peut également faire gagner beaucoup de temps à
l'opérateur.
8.2.14 Centrifugeuse, pouvant contenir les flacons centrifuges de 300 ml (voir 8.7).
8.2.15 Éprouvette graduée de 100 ml.
8.2.16 Pipette de 25 ml.
8.2.17 Entonnoir de filtration en verre, pouvant contenir le tamis de 0,063 mm.
8.2.18 Pissette contenant de l'eau (8.3).
8.2.19 Tige, de verre ou de plastique rigide, de 150 mm à 200 mm de longueur et de diamètre d’au moins 4 mm,
avec un manchon de caoutchouc à une extrémité.
8.2.20 Plaque chauffante électrique, pouvant maintenir une température de 105 °C à 110 °C.
NOTE La plaque chauffante est nécessaire si des flacons à centrifuger en polymères sont utilisés pour le traitement chimique
préalable, mais un bec Bunsen, une toile métallique et un trépied sont suffisants si l'on utilise des béchers en verre.
8.2.21 Dispositif d'aspiration, similaire à celui montré à la figure 6 (accessoire utile mais non essentiel).
1 Vers le vide 3 Pipette Pasteur ou similaire
2 Tube flexible 4 Réservoir (5 l ou 10 l)
Figure 6 — Schéma d'un dispositif d'aspiration
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8.2.22 Pinceau pour tamis.
8.2.23 Conductimètre, précis à 0,1 dS/m.
8.3 Réactifs
Tous les réactifs doivent être de qualité analytique reconnue. Utiliser une eau conforme à la classe 2 (ou mieux)
conformément à l'ISO 3696, c'est-à-dire dont la conductivité électrique n'est pas supérieure à 0,1 dS/m à 25 °C au
moment de l'utilisation.
8.3.1 Solution de peroxyde d'hydrogène, à 30 % (fraction volumique).
NOTE Une solution à 30 % (fraction volumique) est une solution qui dégage 30 ml d'oxygène à partir de 100 ml de solution
(dans des conditions normales de température et de pression) au moment de la réduction en eau, par des moyens chimiques,
ou par ébullition.
8.3.2 Solution de dispersant.
La plus répandue est celle préparée en dissolvant 33 g d'hexamétaphosphate de sodium et 7 g de carbonate de
sodium anhydre dans de l'eau pour faire 1 litre de solution. Ceci est le dispersant recommandé. Le stocker à l'abri
de la lumière et de préférence dans un flacon coloré. Enregistrer la date de préparation sur le flacon. La solution est
instable et doit être remplacée au bout de 1 mois.
Dans la documentation, l'hexamétaphosphate de sodium tamponné est généralement nommé «Calgon». Ceci est
un nom commercial. La substance vendue sous ce nom commercial n'est généralement pas le réactif décrit dans
cette partie, mais d'une composition variable et ne doit pas être utilisée comme agent dispersant dans la présente
Norme internationale [11].
Il est possible d'utiliser d'autres agents dispersants (voir note), dont le choix doit être enregistré dans le rapport
d'essai (article 10). Quel que soit le dispersant qui s'avère le mieux adapté à un sol particulier, il est essentiel que la
suspension soit examinée pour garantir qu'une dispersion effective s'est produite et que la suspension dispersée
est stable, c'est-à-dire qu'aucune floculation ne s'est produite ou ne se produit. Cette inspection doit être effectuée
pour chaque échantillon.
NOTE Le carbonate de sodium tamponne la solution, et la suspension de terre, à environ pH 9,8. Cet agent dispersant s'est
avéré réussir avec une très large gamme de sols. Cependant, si des signes indiquent que la dispersion n'est pas effective,
envisager d'abord que des sels provoquant la floculation peuvent être présents (voir 8.7). Si la dispersion ne se produit
toujours pas après l'élimination des sels, d'autres agents dispersants doivent être pris en considération. Un agent dispersant
très efficace, mais moins largement utilisé, est préparé en remplaçant le carbonate de sodium par une solution ammoniacale à
20 % de fraction volumique, avec un rapport de 5 ml de solution ammoniacale pour 150 ml de solution d'hexamétaphosphate. Il
existe de nombreux autres agents dispersants [2]. Quel que soit celui qui est choisi, une recherche considérable est exigée
pour établir son efficacité. Il convient de se souvenir que certains sols posent moins de problèmes de dispersion s'ils sont
analysés sans séchage (annexe A). Certains sols dérivés de dépôts volcaniques récents se dispersent plus efficacement dans
un milieu acide [12].
8.3.3 Octane-2-ol, ou un agent antimousse volatil similaire.
NOTE L'octane-2-ol est très efficace et son effet est relativement long. L'éthanol ou le méthanol peuvent également être
utilisés, mais l'utilisation de pentane-2-ol (alcool isoamylique) est déconseillée parce qu'il peut créer une accoutumance
physiologique.
8.4 Étalonnages
8.4.1 Pipette de prélèvement (voir figure 4)
Nettoyer et sécher soigneusement la pipette et immerger la pointe dans de l'eau maintenue à la même température
que l'enceinte thermostatée (8.2.2). Avec un tube fixé sur C, aspirer l'eau dans la pipette au-dessus de E. Vider
l'eau au-dessus de E jusqu'à F. Vider la pipette dans un flacon de pesée préalablement taré et déterminer la
nouvelle masse. À partir des masses connues, calculer le volume interne de la pipette. Répéter cette opération trois
fois et prendre la moyenne des trois volumes comme volume interne de la pipette, à 0,05 ml près (V ml).
c
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8.4.2 Correction de la masse de dispersant
Suivre ce mode opératoire à chaque fois qu'une nouvelle solution de dispersant est préparée.
Ajouter à la pipette 25 ml de solution de dispersant dans un des tubes de sédimentation en verre, et remplir le tube
jusqu'au trait de jauge de 500 ml avec de l'eau. Mélanger soigneusement le contenu du tube. Placer le tube dans
l'enceinte thermostatée pendant au moins 1 h. Choisir un temps de prélèvement (voir tableau 3), prélever un
échantillon (V ml) de la solution d'agent dispersant dans le tube de sédimentation en utilisant la pipette de
c
prélèvement. Vider la pipette dans un cristallisoir de pesée taré, et sécher le contenu de la cuve entre 105 °C et
110 °C. Laisser refroidir dans un dessiccateur et déterminer la masse du résidu à 0,000 1 g près (m ).
r
NOTE La durée minimale de mise à température dans le bain-marie est de 1 h, mais si un plus grand nombre de tubes est
placé dans un bain, la mise à l'équilibre prendra au moins 4 h. Dans ce cas, il est avantageux d'organiser le travail de façon
que la mise à température ait lieu la nuit. Elle sera plus rapide si l'eau utilisée pour remplir les tubes est à la même ou quasi la
même température que l'enceinte thermostatée.
8.5 Prise d'essai
La prise d'essai doit être prélevée sur la fraction d'échantillon inférieure à 2 mm (article 6 et 7.3) et pesée à 0,001 g
près (m ). La masse de la prise d'essai dépend du type de sol. Environ 30 g pour un sol sableux et 10 g pour un sol
s
argileux conviennent pour une analyse par pipette, avec une prise d'essai adaptée pour les sols se situant entre ces
extrêmes. Pour la méthode du densimètre (annexe B), prendre deux fois cette quantité. Placer la prise d'essai dans
le bécher en verre de 650 ml ou le flacon à centrifuger de 300 ml (8.2.13 et sa note).
NOTE Les sols très organiques contiennent relativement peu de matière minérale. Il peut être nécessaire de prendre jusqu'à
100 g de sol afin d'obtenir suffisamment de matière minérale pour qu'une analyse soit fiable. Une telle quantité d'échantillon
doit être répartie entre plusieurs béchers pour faciliter la destruction de la matière organique, les résidus minéraux étant
rassemblés par la suite.
8.6 Destruction de la matière organique
Détruire la matière organique avec la solution de peroxyde d'hydrogène, comme suit. Ajouter environ 30 ml d'eau à
la prise d'essai et laisser l'échantillon s'humecter (voir note 1 ci-dessous). Ajouter 30 ml de solution de peroxyde
d'hydrogène à 30 % de fraction volumique et mélanger le contenu du bécher très doucement en utilisant la tige de
verre ou de plastique. Des réactions vigoureuses peuvent entraîner une effervescence. Ce phénomène peut être
contrôlé par l'ajout de quelques millilitres d'octane-2-ol. Laisser ces réactions s'atténuer.
AVERTISSEMENT — Cette étape doit être effectuée avec précaution. Le peroxyde d'hydrogène peut se
décomposer violemment avec certaines formes de matière organique, certains composés de manganèse et
les sulfures ferreux à particules fines pouvant être présents dans le sol. En aucune circonstance la réaction
dans le bécher ne doit être examinée de dessus, et une réaction apparemment lente ne doit pas non plus
être accélérée par chauffage ou ajout de peroxyde d'hydrogène.
En cas d'utilisation d'un bécher de 650 ml, couvrir ce dernier d'un verre de montre et laisser reposer toute la nuit.
Placer le bécher sur la plaque chauffante ou le bec de Bunsen (conformément à 8.2.20) et chauffer doucement.
Contrôler toute effervescence avec l'octane-2-ol comme précédemment, et agiter fréquemment le contenu. Ne pas
le laisser aller à sec, ajouter de l'eau si nécessaire. Amener la suspension à ébullition modérée et chauffer jusqu'à
ce que l'effervescence ait cessé. S'il reste de la matière organique non décomposée, retirer le bécher de la chaleur,
le laisser refroidir et répéter le traitement avec du peroxyde d'hydrogène. Les sols très organiques ont besoin de
plusieurs traitements de ce type, les produits de la réaction étant éliminés tous les 2 ou 3 traitements avant de
rajouter du peroxyde.
Si la destruction de la matière organique a été effectuée dans un flacon à centrifuger, compléter le contenu entre
150 ml et 200 ml par ajout d'eau. Si un bécher en verre a été utilisé, transférer le contenu dans un flacon à
centrifuger en prenant soin de retirer toute trace de matière sur les parois du bécher avec le manchon de
caoutchouc de la tige de verre ou de plastique. Là également, le volume final doit être de 150 ml à 200 ml.
Centrifuger le flacon afin d'obtenir un surnageant clair [15 min à une force centrifuge relative minimale (FCR) de
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400 g est recommandé (g étant l'accélération due à la pesanteur)] et éliminer ce dernier par transvasement ou avec
un dispositif d'aspiration. Répéter le traitement jusqu'à ce que le surnageant soit incolore ou presque.
NOTE 1 Les matières organiques sèches sont souvent fortement hydrophobes. Il peut être avantageux dans ce cas d'ajouter
quelques gouttes d'octane-2-ol.
Si une centrifugeuse n'est pas disponible, les résidus minéraux peuvent être floculés en ajoutant 25 ml de solution
de chlorure de calcium à 1 mol/l. Mélanger soigneusement, compléter à environ 250 ml avec de l'eau, laisser
reposer jusqu'à ce que le surnageant soit clair, ensuite siphonner ou transvaser pour récupérer le résidu solide.
Ajouter 250 ml d'eau supplémentaire et répéter la procédure de lavage jusqu'à ce que les résidus foncés de la
matière organique décomposée aient disparu. Vérifier que la conductivité électrique des solutions de lavage est
inférieure à 0,4 dS/m avant d'essayer de disperser le résidu (8.8).
Une autre possibilité consiste à filtrer le résidu après la phase d'oxydation sur un papier-filtre à haute résistance à
l'état humide (une porosité de 2,7 μm convient), puis à le laver soigneusement avec de l'eau, au moyen d'une
pissette. Il est essentiel d'observer le filtrat de près pour voir s'il n'y a pas de perte. Si des particules sont passées à
travers le papier-filtre, remettre le filtrat dans le récipient, ajouter une solution de chlorure de calcium à la
suspension comme ci-dessus, mélanger et filtrer de nouveau.
Si la floculation avec le chlorure de calcium, ou la filtration sont inefficaces pour empêcher la perte de particules
fines de sol, quelques gouttes de soluti
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