SIST-TS CEN ISO/TS 17892-9:2004
(Main)Geotechnical investigation and testing - Laboratory testing of soil - Part 9: Consolidated triaxial compression tests on water saturated soil (ISO/TS 17892-9:2004)
Geotechnical investigation and testing - Laboratory testing of soil - Part 9: Consolidated triaxial compression tests on water saturated soil (ISO/TS 17892-9:2004)
This document covers the determination of stress-strain relationships and effective stress paths for a cylindrical, water-saturated ) specimen of undisturbed, remoulded or reconstituted soil when subjected to an isotropic or an anisotropic stress under undrained or drained conditions and thereafter sheared under undrained or drained conditions within the scope of the geotechnical investigations according to prEN 1997 1 and 2. The test methods provide data that are appropriate to present tables and plots of stress versus strain, and effective stress paths.
Special procedures such as:
a) Tests with lubricated ends;
b) tests with local measurement of strain or local measurement of pore pressure;
c) tests without rubber membranes;
d) extension tests;
e) shearing where cell pressure varies;
f) shearing at constant volume (no pore pressure change)
are not covered.
The conventional triaxial apparatus is not well suited for measurement of the initial moduli at very small strains. However, strains halfway up to failure are considered to be large enough to be measured in conventional triaxial cells.
Geotechnische Erkundung und Untersuchung - Laborversuche an Bodenproben - Teil 9: Konsolidierte triaxiale Kompressionsversuche an wassergesättigten Böden (ISO/TS 17892-9:2004)
Diese Technische Spezifikation legt das Verfahren zur Bestimmung der Spannungs-Dehnungs-Beziehungen und der wirksamen Spannungspfade an einem zylindrischen, wassergesättigten ) Probekörper aus ungestörtem oder aufbereitetem Boden, der einem isotropen oder anisotropen Spannungszustand unter dränierten oder undränierten Bedingungen ausgesetzt und anschließend unter undränierten oder dränierten Bedingungen abgeschert wird nach ENV 1997-1 und ENV 1997-2 fest. Die Versuchsergebnisse können tabellarisch oder als Spannungs-Dehnungs-Kurven sowie als Spannungspfade dargestellt werden.
Besondere Verfahren wie
a) Versuche mit geschmierten Endflächen;
b) Versuche mit lokaler Messung der Verformungen oder des Porenwasserdrucks;
c) Versuche ohne Gummihülle;
d) Extensionsversuche;
e) Abscheren mit veränderlichem Zellendruck;
f) Abscheren bei konstantem Volumen (ohne Porenwasserdruckänderung)
werden nicht behandelt.
Konventionelle Triaxialgeräte sind nicht geeignet, Anfangsmoduli bei sehr kleinen Verformungen zu messen. Allerdings kann man davon ausgehen, dass die Verformungen bis etwa zur halben Bruchspannung groß genug sind, um sie auch in konventionellen Triaxialzellen messen zu können.
Reconnaissance et essais géotechniques - Essais de laboratoire sur les sols - Partie 9: Essai en compression a l'appareil triaxial sur sols saturés consolidés (ISO/TS 17892-9:2004)
Cette Spécification Technique concerne la détermination des relations contrainte-déformation et des chemins de contraintes effectives, pour une éprouvette cylindrique, saturée d'eau, constituée de sol non remanié, remanié ou reconstitué, lorsqu'elle est soumise a une contrainte isotrope ou anisotrope, dans des conditions drainées ou non drainées, et qu'elle est ensuite cisaillée, dans des conditions drainées ou non drainées selon le domaine d'application des reconnaissances géotechniques conforme aux Parties 1 et 2 de ENV 1997. Ces méthodes d'essais permettent de fournir des tableaux de données, des courbes de contraintes en fonction des déformations et des courbes de chemins de contraintes effectives.
Les procédures particulieres suivantes ne sont pas couvertes :
a) essais avec des embases lubrifiées ;
b) essais avec une mesure locale de la déformation ou une mesure locale de la pression interstitielle ;
c) essais sans membrane de caoutchouc ;
d) essais en extension ;
e) cisaillement avec variations de la pression cellulaire ;
f) cisaillement a volume constant (sans variation de la pression interstitielle).
L'appareillage triaxial conventionnel n'est pas bien adapté pour la détermination du module a l'origine pour de tres petites déformations. Cependant des déformations a mi-chemin de la rupture sont considérées comme suffisamment grandes pour etre mesurées avec des cellules triaxiales conventionnelles
Geotehnično preiskovanje in preskušanje - Laboratorijsko preskušanje zemljin - 9. del: Konsolidiran triosni tlačni preskus na z vodo zasičenih zemljinah (ISO/TS 17892-9:2004)
Ta dokument zajema ugotavljanje razmerja med napetostjo in deformacijo ter efektivnih napetostnih poti za valjaste z vodo zasičene vzorce nespremenjenih, preoblikovanih ali rekonstituiranih zemljin, na katere deluje izotropna ali anizotropna napetost pod nedreniranimi ali dreniranimi pogoji, nato pa se strižejo pod nedreniranimi ali dreniranimi pogoji v okviru geotehničnih preiskav v skladu s prEN 1997-1 and -2. Preskusne metode zagotavljajo podatke, primerne za predstavitev v preglednicah in krivuljah deformacije v odvisnosti od napetosti ter efektivnih napetostnih poti. Posebni postopki, kot so: a) preskusi s premazanimi konci; b) preskusi z lokalnim merjenjem deformacije ali lokalnim merjenjem pornega tlaka; c) preskusi brez gumenih membran; d) razširitveni preskusi; e) striženje, kadar se celični tlak spreminja; f) striženje pri stalnem volumnu (brez spreminjanja pornega tlaka), niso zajeti. Konvencionalni triosni aparat ni primeren za meritve začetnih modulov pri zelo majhnih deformacijah. Deformacije, ki so na pol poti do razpada, pa veljajo za dovolj velike, da se lahko merijo v konvencionalnih triosnih celicah.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS CEN ISO/TS 17892-9:2004
01-december-2004
*HRWHKQLþQRSUHLVNRYDQMHLQSUHVNXãDQMH/DERUDWRULMVNRSUHVNXãDQMH]HPOMLQ
GHO .RQVROLGLUDQWULRVQLWODþQLSUHVNXVQD]YRGR]DVLþHQLK]HPOMLQDK ,6276
Geotechnical investigation and testing - Laboratory testing of soil - Part 9: Consolidated
triaxial compression tests on water saturated soil (ISO/TS 17892-9:2004)
Geotechnische Erkundung und Untersuchung - Laborversuche an Bodenproben - Teil 9:
Konsolidierte triaxiale Kompressionsversuche an wassergesättigten Böden (ISO/TS
17892-9:2004)
Reconnaissance et essais géotechniques - Essais de laboratoire sur les sols - Partie 9:
Essai en compression a l'appareil triaxial sur sols saturés consolidés (ISO/TS 17892-
9:2004)
Ta slovenski standard je istoveten z: CEN ISO/TS 17892-9:2004
ICS:
13.080.20 Fizikalne lastnosti tal Physical properties of soils
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
SIST-TS CEN ISO/TS 17892-9:2004 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TS CEN ISO/TS 17892-9:2004
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SIST-TS CEN ISO/TS 17892-9:2004
TECHNICAL SPECIFICATION
CEN ISO/TS 17892-9
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
October 2004
ICS 13.080.20; 93.020
English version
Geotechnical investigation and testing - Laboratory testing of
soil - Part 9: Consolidated triaxial compression tests on water
saturated soil (ISO/TS 17892-9:2004)
Reconnaissance et essais géotechniques - Essais de sol Geotechnische Erkundung und Untersuchung -
au laboratoire - Partie 9 : Essai triaxial consolidé sur sols Laborversuche an Bodenproben - Teil 9: Konsolidierte
saturés (ISO/TS 17892-9:2004) triaxiale Kompressionsversuche an wassergesättigten
Böden (ISO/TS 17892-9:2004)
This Technical Specification (CEN/TS) was approved by CEN on 2 February 2004 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TS 17892-9:2004: E
worldwide for CEN national Members.
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Contents
page
Foreword.3
1 Scope .5
2 Normative References.5
3 Terms and definitions .5
4 Symbols .7
5 Equipment .7
5.1 General.7
5.2 Triaxial cell .8
5.3 Confining membrane.9
6 Test procedure.11
6.1 General requirement and equipment preparation.11
6.2 Preparation of undisturbed specimens.12
6.3 Artificially prepared specimens .12
7 Test results.18
7.1 Bulk density, dry density and water content .18
7.2 Consolidation.18
7.3 Shearing (all types of test).18
8 Test report .22
8.1 General.22
8.2 Graphic presentation.23
Bibliography .24
Figures
Figure 1 — Mohr stress circles at failure .6
Figure 2 — Example of a triaxial test unit .8
2
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Foreword
This document (CEN ISO/TS 17892-9:2004) has been prepared by Technical Committee CEN/TC 341
“Geotechnical investigation and testing”, the secretariat of which is held by DIN, in collaboration with Technical
Committee ISO/TC 182 “Geotechnics”.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Cyprus, Czech Republic, Denmark,
Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
CEN ISO/TS 17892 consists of the following parts, under the general title Geotechnical investigation and testing —
Laboratory testing of soil:
Part 1: Determination of water content.
Part 2: Determination of density of fine grained soil.
Part 3: Determination of particle density - Pycnometer method.
Part 4: Determination of particle size distribution.
Part 5: Incremental loading oedometer test.
Part 6: Fall cone test.
Part 7: Unconfined compression test on fine-grained soils.
Part 8: Unconsolidated undrained triaxial test.
Part 9: Consolidated triaxial compression tests.
Part 10: Direct shear tests.
Part 11: Permeability tests.
Part 12: Determination of Atterberg limits.
3
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Introduction
This document covers areas in the international field of geotechnical engineering never previously standardised. It
is intended that this document presents broad good practice throughout the world and significant differences with
national documents is not anticipated. It is based on international practice (see [1]).
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1 Scope
This document covers the determination of stress-strain relationships and effective stress paths for a cylindrical,
1)
water-saturated specimen of undisturbed, remoulded or reconstituted soil when subjected to an isotropic or an
anisotropic stress under undrained or drained conditions and thereafter sheared under undrained or drained
conditions within the scope of the geotechnical investigations according to prEN 1997-1 and -2. The test methods
provide data that are appropriate to present tables and plots of stress versus strain, and effective stress paths.
Special procedures such as:
a) Tests with lubricated ends;
b) tests with local measurement of strain or local measurement of pore pressure;
c) tests without rubber membranes;
d) extension tests;
e) shearing where cell pressure varies;
f) shearing at constant volume (no pore pressure change)
are not covered.
The conventional triaxial apparatus is not well suited for measurement of the initial moduli at very small strains.
However, strains halfway up to failure are considered to be large enough to be measured in conventional triaxial
cells.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including any
amendments) applies.
prEN 1997-2, Eurocode 7: Geotechnical design - Part 2: Design assisted by laboratory testing
prEN 1997-1, Eurocode 7: Geotechnical design - Part 1: General rules
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
CIU-test
isotropically consolidated undrained test
3.2
CAU-test
anisotropically consolidated undrained test
3.3
CID-test
isotropically consolidated drained test
1) Water saturated refers to the in-situ condition. The material tested need not necessarily be saturated at all stages during the
laboratory testing.
5
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3.4
CAD-test
anisotropically consolidated drained test
3.5
back pressure
external pressure by which the pore pressure is increased prior to consolidation or shearing in order to saturate the
filters, the pore pressure measuring system and the specimen
3.6
failure
stress or strain condition at which failure takes place
NOTE If no specification for the failure state is given, failure may be considered to occur at the peak deviator stress.
3.7
effective shear strength parameter
friction angle φ ' and cohesion intercept c' both in terms of effective stress (see Figure 1)
NOTE These parameters relate to the shear stress mobilized at the failure state specified.
Key
a Test 1
b Test 2
c Test C
X effective normal stress
Y shear stress
c´ effective cohesion intercept
a’ attraction intercept
φ’ effective friction angle
Figure 1 — Mohr stress circles at failure
3.8
cohesive soils
soils that behave as if they were actually cohesive, e.g. clay and clayey soils
NOTE Most soils in this group behave cohesively due to negative pore pressure and friction, and not due to cohesion.
3.9
undisturbed simple
sample of quality class 1 according to prEN 1997-2
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4 Symbols
ε and ε vertical and volumetric strain, respectively, during shearing.
1 vol
σ total cell pressure.
cell
σ and σ ' major total and major effective stress, respectively (see note).
1 1
σ and σ ' minor total and minor effective stress, respectively (see note).
3 3
σ −σ deviator stress.
1 3
u and ∆u total pore pressure and change in pore pressure respectively.
σ ' major effective stress at end of consolidation.
1C
σ ' minor effective stress at end of consolidation.
3C
NOTE Except perhaps in the case of anisotropic consolidation of strongly overconsolidated materials, σ will be equal to
1
the vertical stress and σ will be equal to the horizontal stress for all tests described in this draft. If the vertical stress is greater
3
than the horizontal one, the vertical stress shall be called σ instead of σ and the horizontal stress σ instead of σ .
V 1 H 3
5 Equipment
5.1 General
A schematic diagram of an apparatus for triaxial testing is shown in Figure 2.
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Key
1 alternative positions for load measuring device
2 air bleed
3 vertical compression measuring device
4 piston
5 top cap
6 soil specimen
7 membrane
8 pedestal
9 device for measurement and control of cell pressure
10 triaxial cell
11 drainage tubes
12 pore pressure sensor
13 volume change sensor
14 device for measurement and control of back pressure
P vertical load
Figure 2 — Example of a triaxial test unit
5.2 Triaxial cell
5.2.1 The triaxial cell shall be able to withstand a total cell pressure equal to the sum of the consolidation stress
and the back pressure without significant of cell fluid out of the cell.
A cell with a maximum cell pressure of 2000 kPa will be sufficient for nearly all cases. Transparent cells should be
used.
5.2.2 The sealing bushing and piston guide shall be designed such that the piston runs smoothly and maintains
alignment.
5.2.3 The testing procedure, the accuracy of the load measuring device, the design of the piston, its sealing and
guide and the design of the connection between the piston and the top cap shall be such that the load at failure is
known to an accuracy of ± 3 % or to an accuracy of ± 1 N, whichever is the greater. It shall be ensured that this
accuracy can be achieved with the worst possible combination of vertical and horizontal force and bending moment
acting at that end of the piston that projects into the triaxial cell.
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If the load measuring device is situated outside the triaxial cell (see Figure 2), it shall be ensured that the friction
between the piston and its sealing bushing is low enough or repeatable enough to permit the failure load to be
determined with the required accuracy.
NOTE Smooth running of the piston when subjected to no horizontal load and no cell pressure is no guarantee that this is
the case.
If the load measuring device is situated inside the triaxial cell, it shall be ensured that the device is sufficiently
insensitive to horizontal forces and/or bending moments to achieve the required accuracy. The influence of the cell
pressure on the load cell, if any shall be sufficiently repeatable to be corrected for.
5.2.4 The top cap and the pedestal and the connection between the top cap and the piston shall be designed
such that their deformations are negligible compared to the deformations of the soil specimen.
5.2.5 The diameter of the top cap and of the pedestal shall normally be equal to the diameter of the specimen.
Specimens with diameters smaller than the diameter of the end caps may be tested provided cavities under the
membrane at the ends of the specimen can be avoided.
5.2.6 The vertical stress applied on the specimen due to the weight of the top cap shall not exceed 3 % of the
unconfined compressive strength (compressive strength is equal to two times the shear strength) of the specimen
or 1 kPa whichever is the greater.
For cohesionless specimens held together with a suction the unconfined compressive strength in this connection
may be assumed to be equal to the maximum deviator stress the specimen can sustain with the applied suction
without collapsing.
5.2.7 The valves on the drainage tubes coming from the filter discs shall not cause a pressure change greater
than 1 kPa when operated in a closed saturated pore pressure system. All valves shall be able to withstand the
applied pressure without leakage.
Both the top and the pedestal should, preferably, have two drainage tubes so that the filter discs can be flushed
with water after mounting of the specimen.
5.3 Confining membrane
5.3.1 The soil specimen shall be confined by an elastic membrane which effectively prevents the cell fluid from
penetrating into the specimen.
5.3.2 Combinations of confining membranes and filter strips that give a combined correction on the deviator
stress (σ -σ ) of more than 10 % at failure should not be used (see 5.5, 7.4 and 7.5).
1 3
5.3.3 If O-rings are used to seal the confining membrane to the top and to the pedestal, their dimensions and
elastic properties shall be such the confining membrane is firmly sealed to the top cap and to the pedestal.
If rubber membranes are used, membranes with following properties should be used.
unstretched diameter between 95 % and 100 % of specimen (after being stored in water);
thickness not exceeding about 1 % of the specimen diameter;
elastic modulus (measured in tension) not exceeding 1600 kPa.
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5.4 Porous discs
5.4.1 The diameter of the porous discs at the ends of the soil specimen shall be equal to that of the specimen.
The discs have a plane and smooth surface and their compression shall be negligible compared to the
compression of the soil specimen.
5.4.2 The coefficient of permeability of the porous discs shall for tests on clay and silt specimens be between
- 6 ' -4
10 m/s and 10 m/s. For tests on coarser materials more permeable porous discs should be used.
5.4.3 The discs should be boiled in distilled water for 10 minutes before use and kept immersed in de-aired water
until required.
5.5 Filter paper
5.5.1 Filter paper for side drain shall be of a type which does not dissolve in water and has a coefficient of
-7
permeability not less than 10 m/s for a normal pressure of 600 kPa.
-9
Filter paper strips should not be used for soils with a coefficient of permeability equal to and higher than about 10
m/s.
5.5.2 To avoid hoop tension, vertical filter paper strips shall not cover more than 50 % of the specimen periphery.
NOTE No correction for filter paper strength is needed if only four, inclined filter paper strips are used where the width of
each strip does not exceed about 10 % of the specimen diameter and where the inclination of each strip is about 1:√2, 1 being
the vertical distance √2 the corresponding distance along the specimen perimeter.
5.5.3 Filter paper discs (of the same type as for the side drain) may be used between the specimen and the end
porous discs in cases where soil particles tend to be washed through the discs.
5.6 Fluid pressure devices
The devices for keeping the cell and the pore pressure constant shall be accurate enough to keep the difference
between cell and pore pressure during consolidation constant to within ± 2 % of the required value or within ± 1,0
kPa, whichever is the greater. The tubings between the triaxial cell and the pressure measuring device shall be
wide enough to ensure negligible pressure difference between these two components.
5.7 Load frame
5.7.1 The load frame shall be able to provide the rates of vertical strain specified in 6.8.2 and 6.8.3 . The actual
rate shall not deviate more than ± 10 % from the required value. The movement of the platen shall be smooth
without fluctuations or vibrations.
A load frame with a maximum load capacity of 15 kN which is able to advance to the piston with rates varying from
about 0,0005 to about 2 mm per minute with a minimum of ten different advance rates is considered to be sufficient
for most testing on material more fine-grained than gravel.
5.7.2 The stroke of the load frame shall be at least 30 % of the specimen height.
5.8 Measuring devices
5.8.1 Vertical load
The accuracy of the vertical load sensor shall be compatible with the accuracy by which the failure load is required
to be known (see 5.2.3).
5.8.2 Pressure
5.8.2.1 Cell pressure and pore pressure measuring devices shall be sufficiently accurate to permit the
difference between total cell pressure and pore pressure to be known within ± 2 % or within ± 1,0 kPa whichever is
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the greater. These devices shall indicate correct pressures at the level corresponding approximately to the half
height of the specimen.
5.8.2.2 The pore pressure system shall be sufficiently rigid. The requirement expressed by equation (1) below
should be used as a guide to the maximum permitted volumetric expansion when pressurised:
∆V
ms −6 2
≤ 0,5 ×10 m / kN (1)
∆V × ∆u
where
∆V is the (∆V ) + (∆V ) (2)
ms tubings ms ppm
ms
( ∆V ) is the change in volume of tubings due to a pore pressure change ∆u. This includes
ms tubings
all tubings which are subjected to pore pressure change during undrained shearing;
( ∆V ) is the change in volume of the pore pressure measuring device (e. g., an electronic sensor)
ms ppm
due to a pore pressure change ∆u;
V is the total volume of specimen.
5.8.3 Compression
5.8.3.1 The vertical displacement of the specimen is usually determined by measuring the distance the piston
travels relative to the cell. The distance travelled by the piston shall be measured with an accuracy better than ±
0,10 % of the initial specimen height.
5.8.3.2 The displacement sensor, with the applied reading equipment, shall be readable to ± 0,015 % of the
initial specimen height.
5.8.3.3 Possible false displacement due to cell pressure change shall be accounted for.
5.8.3.4 If stress-strain moduli are to be measured, the accuracy of the compression measurement shall be
adjusted to be compatible with the desired accuracy for the measurement of the stress-strain moduli.
5.8.4 Volume change
The amount water and air going into or out of the specimen shall be measured with an accuracy better than
± 0,20 % of the initial volume of the specimen. The volume change sensor, with the applied reading equipment,
shall be readable to ± 0,05 % of the initial volume of the specimen.
6 Test procedure
6.1 General requirement and equipment preparation
6.1.1 Test specimen shall be cylindrical with diameter not less than 35 mm and height from 1,85 to 2,25 times
the diameter. For materials with uniform grading (i. e. materials with uniformity coefficient C = d /d <5), the
u 60 10
largest soil particle size should not exceed 1/10 of the specimen diameter. For other materials the largest particle
size may be up to 1/6 of the specimen diameter.
6.1.2 The specimen height and diameter shall be measured or evaluated in such a way their average values are
known within ± 0,1 mm. The mass of the specimen shall be measured to within ± 0,1%.
6.1.3 Care shall be taken to maintain the water content of the specimen during the preparation process. If the
process for some reason is interrupted, the specimen shall be carefully wrapped in plastic foil. Air circulation
around the specimen shall be avoided.
6.1.4 It shall be checked prior to each test that the drainage tubes and valves are not clogged and are without
leakage are without leakage when pressurized.
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6.1.5 The confining membrane shall be checked for leakage before each test, for example by subjecting it to a
small air pressure on the inside and looking for air bubbles when immersing it in water. The membranes shall be
dry on the inside before being placed onto the soil specimen.
If rubber membranes are used, they shall be stored in water at least 24 hours before being used because dry
membranes tend to adsorb water.
6.1.6 The filter discs shall be regularly checked to determine whether they have become clogged.
A filter disc may be checked for clogging in the following way: tape shall be mounted along the perimeter of the
filter, some water is placed on top of it and air is blown upwards through the filter. The operation shall be repeated
with a new, unused filter for comparison.
6.1.7 When the set up is ready for the triaxial cell to be mounted, a small suction, (5 kPa to 50 kPa, low enough
not to cause any harm to the specimen) shall be applied to the drainage tubes. The vacuum shall then be shut off.
If the vacuum decreases more than about 2 % over a time period of about 2 minutes, investigations shall be made
to detect possible leaks in the membrane or drainage tubes.
6.1.8 If the vertical load is measured outside the triaxial cell, it shall be checked prior to each test that the piston
runs smoothly, and if a rotation bushing is used, it shall be checked during each test, by direct observation of the
bushing, preferably at high loads, that it really rotates.
6.1.9 To fill the cell, a liquid shall be used which does not significantly penetrate the membrane enclosing the
specimen or absorb a significant amount of water from the specimen through the membrane.
NOTE De-aired water is generally found to meet these requirements.
6.1.10 The water used to saturate (or flush) filter discs and filter papers shall be de-aired. If the salt content of the
pore water is known, filter discs and filter papers should be saturated (or flushed) using water with this known salt
content. If the salt content is unknown, fresh water shall be used.
6.2 Preparation of undisturbed specimens
6.2.1 Disturbed material near the ends of a sample should not be used for triaxial testing.
6.2.2 Extreme care shall be take to avoid, as much as possible, deforming the specimen during the mounting
process. Very soft specimens (undrained shear strength < 12,5 kPa) may have to be mounted without touching the
specimen by hand at any stage during the preparation.
6.2.3 The end surfaces shall be plane and perpendicular to the longitudinal axis as possible. The angle between
each end surface and the longitudinal axis shall not deviate from a right angle by more than ± 0,6°. Grooves and
holes in the ends and sides of the specimen shall be filled with remoulded material if they cannot be removed by
further trimming and if new specimens cannot be trimmed. Grooves and holes in the ends greater than 1/10 of
specimen diameter shall be filled in with a material that hardens with time and which does not release or absorb
water.
6.2.4 Undisturbed clay and clayey specimens shall be prevented from swelling caused by the specimen sucking
water from the filter discs (see note). Exception from the requirement to prevent swelling can only be made if it can
be documented that the swelling occurring does not lead to significant softening of the specimen.
NOTE The safest method to achieve this is to mount the specimen with dry filter discs and to flush them with water with a
cell pressure high enough to inhibit swelling. The procedure is recommended especially for specimens that may swell
appreciably when in contact with water.
6.3 Artificially prepared specimens
6.3.1 Remoulded or reconstituted specimens may be prepared by tamping/kneading /vibrating the material in
layers into a split mould with the rubber membrane mounted inside (see note). The top of each layer should be
scarified prior to the addition of material of the next layer. Water mixed into the material should be given time
before the compaction to equalize over the whole soil mass. Under-compaction should be used (except for
remoulded specimens) to achieve a homogeneous specimen. Specimens of noncohesive material may be held
together by a negative pore pressure of 10 kPa to 20 kPa when the split mould is removed, until a positive cell
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SIST-TS CEN ISO/TS 17892-9:2004
CEN ISO/TS 17892-9:2004 (E)
pressure of equal magnitude has been applied. Reconstituted specimens of sand may also be prepared by pluvial
compaction (sand raining) in air or under water.
NOTE Remoulded specimens are specimens made of cohesive remoulded material at a water content near the in situ
water content.
6.3.2 If the specimen is to be saturated (or flushed) with water after mounting de-aired water shall be used. A dry
soil containing its natural salt content shall be flushed with fresh water. For tests where a high degree of water
saturation is necessary to me
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