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
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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
ISO 11277:1998(E)
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ISO 11277:1998(E)
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
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X.400 c=ch; a=400net; p=iso; o=isocs; s=central
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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ISO 11277:1998(E) ISO
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.).
6
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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ISO 11277:1998(E)
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:
2
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
3
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
3
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
1
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:
1
proportion retained on the 20 mm sieve = [m(20 mm)]/m
1
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:
1
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).
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 °
...
SLOVENSKI STANDARD
SIST ISO 11277:2006
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
SIST ISO 11277:2006 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 11277:2006
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SIST 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
ISO 11277:1998(E)
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SIST ISO 11277:2006
ISO 11277:1998(E)
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
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Internet central@iso.ch
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Printed in Switzerland
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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.).
6
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:
2
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
3
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
3
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
1
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:
1
proportion retained on the 20 mm sieve = [m(20 mm)]/m
1
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:
1
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).
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 an
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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
ISO 11277:1998(E)
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oSIST ISO 11277:2006
ISO 11277:1998(E)
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
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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.).
6
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:
2
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
3
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
3
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
1
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:
1
proportion retained on the 20 mm sieve = [m(20 mm)]/m
1
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:
1
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).
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 cyl
...
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
ISO 11277:1998(F)
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ISO 11277:1998(F)
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
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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.
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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.
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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.
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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.).
6
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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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:
2
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);
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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
3
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
3
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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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
1
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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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:
1
proportion retenue sur le tamis de 20 mm = [m(20 mm)]/m
1
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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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
...
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