EN ISO 17892-9:2018

SLOVENSKI STANDARD
01-junij-2018
1DGRPHãþD
SIST-TS CEN ISO/TS 17892-9:2004
SIST-TS CEN ISO/TS 17892-9:2004/AC:2010
*HRWHKQLþQRSUHLVNRYDQMHLQSUHVNXãDQMH/DERUDWRULMVNRSUHVNXãDQMH]HPOMLQ
GHO.RQVROLGLUDQWULRVQLWODþQLSUHVNXVQD]YRGR]DVLþHQLK]HPOMLQDK,62

Geotechnical investigation and testing - Laboratory testing of soil - Part 9: Consolidated
triaxial compression tests on water saturated soils (ISO 17892-9:2018)
Geotechnische Erkundung und Untersuchung - Laborversuche an Bodenproben - Teil 9:
Konsolidierte triaxiale Kompressionsversuche an wassergesättigten Böden (ISO 17892-
9:2018)
Reconnaissance et essais géotechniques - Essais de laboratoire sur les sols - Partie 9:
Essais en compression à l'appareil triaxial consolidés sur sols saturés (ISO 17892-
9:2018)
Ta slovenski standard je istoveten z: EN ISO 17892-9:2018
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 17892-9
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2018
EUROPÄISCHE NORM
ICS 13.080.20; 93.020 Supersedes CEN ISO/TS 17892-9:2004
English Version
Geotechnical investigation and testing - Laboratory testing
of soil - Part 9: Consolidated triaxial compression tests on
water saturated soils (ISO 17892-9:2018)
Reconnaissance et essais géotechniques - Essais de Geotechnische Erkundung und Untersuchung -
laboratoire sur les sols - Partie 9: Essais en Laborversuche an Bodenproben - Teil 9: Konsolidierte
compression à l'appareil triaxial consolidés sur sols triaxiale Kompressionsversuche an wassergesättigten
saturés (ISO 17892-9:2018) Böden (ISO 17892-9:2018)
This European Standard was approved by CEN on 2 February 2018.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17892-9:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 17892-9:2018) has been prepared by Technical Committee ISO/TC 182
"Geotechnics" in collaboration with Technical Committee CEN/TC 341 “Geotechnical Investigation and
Testing” the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2018, and conflicting national standards shall
be withdrawn at the latest by October 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes CEN ISO/TS 17892-9:2004.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 17892-9:2018 has been approved by CEN as EN ISO 17892-9:2018 without any
modification.
INTERNATIONAL ISO
STANDARD 17892-9
First edition
2018-02
Geotechnical investigation and
testing — Laboratory testing of soil —
Part 9:
Consolidated triaxial compression
tests on water saturated soils
Reconnaissance et essais géotechniques — Essais de laboratoire sur
les sols —
Partie 9: Essais en compression à l'appareil triaxial consolidés sur
sols saturés
Reference number
ISO 17892-9:2018(E)
©
ISO 2018
ISO 17892-9:2018(E)
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

ISO 17892-9:2018(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 3
5 Apparatus . 5
5.1 General . 5
5.2 Triaxial cell . 7
5.3 Confining membrane . 7
5.4 Porous discs . 7
5.5 Filter paper . 8
5.6 Pressure systems . 8
5.7 Load frame . 8
5.8 Measuring devices. 8
5.8.1 Load measuring device . . 8
5.8.2 Pressure measuring devices . 9
5.8.3 Vertical displacement measuring device . 9
5.8.4 Volume change measuring device . 9
5.9 Cell and back pressure fluids . 9
5.10 Ancillary apparatus . 9
6 Test procedure .10
6.1 General requirements and equipment preparation .10
6.2 Preparation of specimens .10
6.3 Saturation of specimen .11
6.3.1 Saturation . .11
6.3.2 Application of cell and back pressure .12
6.3.3 Saturation checks .12
6.4 Isotropic consolidation (CIU and CID tests) .13
6.5 Anisotropic consolidation (CAU and CAD tests) .13
6.6 End of consolidation.13
6.7 Shearing .13
6.7.1 General.13
6.7.2 Undrained tests (CIU and CAU) .14
6.7.3 Drained tests (CID and CAD) .14
6.8 Dismounting .15
7 Test results .15
7.1 Bulk density, dry density and water content .15
7.2 Calculations of test parameters .16
7.2.1 Height after consolidation .16
7.2.2 Corrected cross sectional area .16
7.2.3 Corrections for elastic membrane .16
7.2.4 Correction for filter paper strips .17
7.2.5 Vertical total stress.17
7.2.6 Vertical effective stress .17
7.2.7 Horizontal total stress .18
7.2.8 Horizontal effective stress .18
7.2.9 Pore pressure change.18
7.2.10 Vertical strain .18
7.2.11 Vertical strain during shear .18
7.2.12 Volumetric strain .18
7.2.13 Volumetric strain during shear .18
ISO 17892-9:2018(E)
8 Test report .19
8.1 Mandatory reporting .19
8.2 Graphical presentation .20
8.3 Optional reporting .20
Annex A (normative) Calibration, maintenance and checks .21
Annex B (informative) Additional calculations for effective shear strength .23
Bibliography .25
iv © ISO 2018 – All rights reserved

ISO 17892-9:2018(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by the European Committee for Standardization (CEN) Technical
Committee CEN/TC 341, Geotechnical investigation and testing, in collaboration with ISO Technical
Committee TC 182, Geotechnics, in accordance with the agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
This first edition of ISO 17892-9 cancels and replaces ISO/TS 17892-9:2004, which has been technically
revised. It also incorporates ISO/TS 17892-9:2004/Cor.1:2006.
A list of all the parts in the ISO 17892 series can be found on the ISO website.
ISO 17892-9:2018(E)
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 Reference [1]).
vi © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 17892-9:2018(E)
Geotechnical investigation and testing — Laboratory
testing of soil —
Part 9:
Consolidated triaxial compression tests on water
saturated soils
1 Scope
This document specifies a method for consolidated triaxial compression tests on water-saturated soils.
This document is applicable to the laboratory determination of triaxial shear strength under
compression loading within the scope of geotechnical investigations.
The cylindrical specimen, which can comprise undisturbed, re-compacted, remoulded or reconstituted
soil, is subjected to an isotropic or an anisotropic stress under drained conditions and thereafter is
sheared under undrained or drained conditions. The test allows the determination of shear strength,
stress-strain relationships and effective stress paths. All stresses and strains are denoted as positive
numerical values in compression.
NOTE 1 This document provides a test for a single specimen. A set of at least three relatable tests are required
to determine the shear strength parameters from these tests. Procedures for evaluating the results are included
in Annex B and, where required, the shear strength parameters are to be included in the report.
Special procedures such as:
a) tests with lubricated ends;
b) multi-stage tests;
c) tests with zero lateral strain (K ) consolidation;
d) tests with local measurement of strain or local measurement of pore pressure;
e) tests without rubber membranes;
f) extension tests;
g) shearing where cell pressure varies,
are not fully covered in this procedure. However, these specific tests can refer to general procedures
described in this document.
NOTE 2 This document fulfils the requirements of consolidated triaxial compression tests for geotechnical
investigation and testing in accordance with EN 1997-1 and EN 1997-2.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO 14688-1, Geotechnical investigation and testing — Identification and classification of soil — Part 1:
Identification and description
ISO 17892-9:2018(E)
ISO 17892-1, Geotechnical investigation and testing — Laboratory testing of soil — Part 1: Determination
of water content
ISO 17892-2, Geotechnical investigation and testing — Laboratory testing of soil — Part 2: Determination
of bulk density
ISO 17892-3, Geotechnical investigation and testing — Laboratory testing of soil — Part 3: Determination
of particle density
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
CIU-test
isotropically consolidated undrained test
3.2
CAU-test
anisotropically consolidated undrained test
3.3
CID-test
isotropically consolidated drained test
3.4
CAD-test
anisotropically consolidated drained test
3.5
pore pressure
pressure of water in the void space within the soil specimen
3.6
back pressure
external pressure by which the pore pressure is increased prior to consolidation or shearing to ensure
saturation
3.7
cell pressure
pressure applied to the cell fluid
3.8
deviator stress
difference between the vertical total stress and the horizontal total stress
3.9
effective stress
difference between the total stress and pore pressure
3.10
failure
stress or strain condition at which one of the following criteria are met:
— peak deviator stress
2 © ISO 2018 – All rights reserved

ISO 17892-9:2018(E)
— peak effective stress ratio i.e. the ratio between the vertical and horizontal effective stress
— a specified deformation criterion e.g. 10 % vertical strain
— other definitions if required
4 Symbols
A initial cross sectional area of the specimen
i
A cross-sectional area of the specimen at any point in time
cor
a cross-sectional area of the piston if an external load cell is used
B pore pressure coefficient i.e. the ratio of the increase in pore pressure, Δu resulting
from an increment of cell pressure, Δσ under undrained conditions
c
D specimen diameter at the end of consolidation
c
D initial specimen diameter
i
D initial internal diameter of the confining membrane (before it is placed on specimen)
m
E elastic modulus of the confining membrane
m
F factor for calculating the rate of displacement of the load frame
f factor relating the vertical strain to the specimen volumetric strain
H specimen height at the end of consolidation
c
H initial height of specimen
i
h distance from the top of the top cap to the mid-height of the specimen
K load (when fully mobilized) carried by filter paper covering a unit length of the speci-
fp
men perimeter
P vertical load reading
P fraction of perimeter covered by filter paper
fp
t initial thickness of the unstressed membrane
m
t time required for 50 % primary consolidation to take place
t time required for 100 % primary consolidation to take place
u pore pressure at the mid height of the specimen
u back pressure (i.e. the pore pressure at start of shearing)
B
V initial volume of specimen
i
v rate of vertical displacement of the load frame during shearing
max
W gravity force acting on the sum of the deadweight hanger (if used), the piston, the top
cap and one half of the soil specimen
ΔH specimen change in height (with compression being a positive numerical value)
ISO 17892-9:2018(E)
ΔH vertical change in height during consolidation, including any vertical change in height
c
during saturation, if measured
Δu change in pore pressure at the mid height of the specimen
ΔV specimen volume change (with a reduction in volume being a positive numerical value)
ΔV volume change up to the end of consolidation
c
Δσ change in cell pressure
c
(Δσ ) correction to horizontal total stress due to membrane restraint
h m
(Δσ ) correction to vertical total stress due to restraint of the filter paper
v fp
(Δσ ) correction to vertical total stress due to membrane restraint
v m
γ unit weight of the cell fluid
ε strain (with compression being a positive numerical value)
ε vertical strain during shear (expressed as a ratio)
sv
ε volumetric strain during shear (expressed as a ratio)
svol
ε vertical strain (expressed as a ratio)
v
ε expected vertical strain at failure (expressed as a ratio)
vf
(ε ) vertical strain of the membrane (expressed as a ratio)
v m
ε volumetric strain
vol
(ε ) volumetric strain of the volume enclosed by the membrane (expressed as a ratio)
vol m
σ cell pressure
c
σ horizontal total stress at the mid height of the specimen (see note)
h
σ′ horizontal effective stress at the mid height of the specimen (see note)
h
σ′ horizontal effective stress at the mid height of the specimen at the end of consolidation
hc
σ vertical total stress at the mid height of the specimen (see note)
v
σ′ vertical effective stress at the mid height of the specimen (see note)
v
σ − σ deviator stress
v h
(σ′ − 2σ′ )/3 mean effective stress
v h
σ′ vertical effective stress at the mid height of the specimen at the end of consolidation
vc
NOTE Throughout this document, effective stresses are indicated by a prime. Vertical and horizontal
directions are indicated by the suffixes “v” and “h” respectively. This convention ensures that the directions of
the action of stress acting on the specimen are clear and independent of their relative magnitudes.
4 © ISO 2018 – All rights reserved

ISO 17892-9:2018(E)
5 Apparatus
5.1 General
The equipment shall undergo regular calibration, maintenance and checks as specified in Annex A.
A schematic diagram of a typical apparatus for triaxial compression testing is shown in Figure 1.
ISO 17892-9:2018(E)
Key
1 alternative positions for load measuring device 10 pedestal
2 air bleed 11 device for measurement and control of cell pressure
3 vertical displacement measuring device 12 triaxial cell
4 piston 13 drainage tubes
5 top cap 14 pore pressure sensor
6 O-rings 15 device for measurement of volume change
7 porous disc 16 device for measurement and control of back pressure
8 soil specimen 17 flushing system
9 membrane (with or without side drains) P vertical load
Figure 1 — Schematic diagram of a typical triaxial apparatus
6 © ISO 2018 – All rights reserved

ISO 17892-9:2018(E)
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 leakage of cell fluid out of the cell. Transparent cells
should be used where possible.
5.2.2 The sealing bushing and piston guide shall be designed such that the piston runs smoothly with
minimal friction and maintains alignment.
5.2.3 The material of the top cap and the pedestal and the connection between the top cap and the
piston shall be such that their deformations are negligible compared to the deformations of the soil
specimen. In the case of stiff soils and if required (see A.3.3) the vertical deformation shall be corrected
for apparatus compliance.
5.2.4 The diameter of the top cap and of the pedestal should 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.
5.2.5 The vertical stress applied on the specimen due to the weight of the top cap should not exceed
2 % of the estimated undrained shear strength of the specimen or 1 kPa, whichever is greater.
5.2.6 The valves on the drainage tubes coming from the porous discs should 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 cap and the pedestal should
preferably have two drainage tubes so that the porous 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.
NOTE Membranes with an elastic modulus of around 1 400 kPa have been found to be suitable.
5.3.2 Combination of confining membrane and side drains that give a combined correction on the
deviator stress of more than 10 % at failure should not be used (see 5.5, 7.2.3 and 7.2.4).
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 that the confining membrane is firmly sealed to the top cap and to the
pedestal.
5.3.4 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 1 % of the specimen diameter.
5.4 Porous discs
5.4.1 Porous discs shall be rigid, non-corrodible and shall have a compressive strength in excess of the
soils to be tested.
ISO 17892-9:2018(E)
5.4.2 The diameter of the porous discs at the ends of the soil specimen should be equal to that of the
specimen. The discs shall have a plane and smooth surface and their compression shall be negligible
compared to the compression of the soil specimen.
5.5 Filter paper
5.5.1 A filter paper (or similar material) may be placed between the specimen and the porous disc in
order to keep fine material from being washed into the porous disc. The filter paper shall not react with
the specimen. New filter paper shall be used for each test.
5.5.2 New filter paper strips (“side drains”) may also be used to enhance drainage from the radial
edges of low permeability specimens. These may be orientated vertically or spirally, i.e. at an oblique
angle. Spiral drains do not require a filter paper correction and are preferred for specimens with an
undrained shear strength below about 50 kPa.
5.5.3 Vertically orientated filter paper strips shall be evenly spaced and shall not cover more than 50 %
of the specimen’s radial surface. Spiral orientated strips shall be equally spaced, should be orientated at
30 ° to 45 ° to the vertical and shall not cover more than 50 % of the specimen’s radial surface.
5.6 Pressure systems
The devices for applying pressure to the cell and to the back pressure system shall be capable of
maintaining a stable pressure either:
— within 1 kPa or 1 % of the absolute pressure, whichever is greater, or
— within 2 kPa or 3 % of the required effective stress, whichever is greater.
Care needs to be taken when testing at low effective stresses, as it may not be possible to meet the first
requirement.
5.7 Load frame
5.7.1 The load frame shall be able to provide a range of rates of vertical strain as required for the test
(see 6.7.2 and 6.7.3). The actual rate applied up to failure shall not fluctuate more than 10 % from the
intended rate. The movement of the platen shall be smooth without vibration such that fluctuations do
not occur in the test results.
NOTE Frames with a load capacity in the range 10 kN to 50 kN which are able to advance the piston with
displacement rates varying from about 0,000 5 mm to about 2 mm per minute with a minimum of 10 different
constant rates have been found to be sufficient for most testing.
5.7.2 The stroke of the load frame shall be more than that required for the test. A value of 30 % of the
specimen height is normally suitable.
5.8 Measuring devices
5.8.1 Load measuring device
The accuracy of the vertical load measuring device, in the range 20 % to 100 % of the capacity of the
device, shall be 1 N or 1 % of the actual value, whichever is greater. The device should be insensitive
to changes in horizontal forces or bending moments, and to changes in temperature or cell pressure
during a test, unless the performance is sufficiently stable that the effect can be corrected.
8 © ISO 2018 – All rights reserved

ISO 17892-9:2018(E)
The capacity of the load measuring device should be chosen so that the failure load is at least 20 % of its
capacity.
NOTE Class 1 load measuring devices to ISO 7500-1 meet this accuracy requirement.
5.8.2 Pressure measuring devices
5.8.2.1 Cell pressure and pore pressure measuring devices shall be sufficiently accurate to permit the
determination of total cell pressure and pore pressure to 1 kPa or 0,5 % of the full range of the device,
whichever is greater.
5.8.2.2 For the shear stage of an undrained test, the pore pressure measuring device and its couplings
shall be sufficiently rigid so that its change in volume shall be negligible.
5.8.3 Vertical displacement measuring device
The device for measuring the change in height of the specimen shall be accurate to 0,1 mm or to 0,1 % of
the initial specimen height, whichever is greater.
5.8.4 Volume change measuring device
The amount of water and air going into or out of the specimen shall be measured with an accuracy of
0,1 % of the initial volume of the specimen or to 0,1 cm , whichever is greater.
5.9 Cell and back pressure fluids
5.9.1 The cell fluid should be selected such that it does not significantly penetrate through the
membrane into the specimen nor extract pore water from the specimen through the membrane.
NOTE De-aired water is generally found to meet these requirements.
5.9.2 The fluid used to saturate (or flush) the porous discs and filter papers shall be de-aired. Tap
water is often used but water with a similar chemistry as the specimen pore water may be used in
circumstances where the results may be affected.
5.9.3 The cell fluid and the fluid used to saturate the specimen should be stabilized to the same
temperature as the test location.
5.10 Ancillary apparatus
The ancillary apparatus consists of:
— balance, accuracy 0,01 g or 0,1 % of the weighed mass, whichever value is greater,
— timer readable to 1 s;
— maximum/minimum thermometer readable to 1 °C;
— apparatus for determination of water content;
The apparatus for the specimen preparation consists of:
— cutting and trimming tools (e.g. a sharp knife, wire saw, spatula, cutting ring, soil lathe);
— steel straight edge, with a maximum deviation from straight of 0,1 % of its length;
— try-square or a jig (e.g. a mitre box) or split mould to ensure that flatness shall be accurate to within
0,5 % of each dimension and that right-angles are within 0,5 ° of true;
ISO 17892-9:2018(E)
— callipers, either analogue or digital, readable to 0,1 mm or 0,1 % of the measured length, whichever
value is greater.
6 Test procedure
6.1 General requirements and equipment preparation
6.1.1 The test specimen shall be cylindrical with a diameter not less than 34 mm and a height from
1,8 to 2,5 times the diameter. The largest particle size should not exceed 1/6 of the specimen diameter.
Specimens of other sizes or height to diameter ratios may be tested using special procedures.
6.1.2 The drainage tubes and valves shall be checked before each test to confirm that they are not
clogged.
6.1.3 Confining membranes should be immersed in water for at least 24 h before being used. The
membranes shall be free of excess surface water on the inside before being placed onto the soil specimen.
6.1.4 The porous discs shall be clean and not clogged.
6.1.5 Prior to each test check that there is no visible sign of damage to any of the equipment and that
the piston runs smoothly.
6.1.6 If leakage of water from the cell or any water line is observed at any time during the test, the test
shall be halted, the pressure removed from the leaking part if necessary and the leak eliminated before
resuming the test. The effect of the leak on the sample shall be evaluated and if detrimental the test may
be judged invalid.
6.1.7 The system may be checked for leaks when the set-up is ready for the triaxial cell to be mounted.
A small suction, (for example 10 kPa but not more than the intended effective stress) may be applied
to the drainage tubes. The vacuum shall then be shut off. If the vacuum decreases over a time period of
about 2 min, efforts should be made to detect and eliminate any leaks in the membrane or drainage tubes.
6.2 Preparation of specimens
6.2.1 The following procedures shall apply to undisturbed, remoulded, re-compacted or reconstituted
samples.
6.2.2 Examine undisturbed samples prior to testing. If significant disturbance is apparent in the
specimen this should be recorded in the test report. Highly disturbed samples will not provide meaningful
results and should not be tested.
6.2.3 Take care to maintain the water content of the specimen during the preparation process. If the
process is interrupted, the specimen shall be protected so that the water content does not change. Air
circulation around the specimen shall be avoided.
6.2.4 Cut and trim the specimen to the required dimensions. Take care to avoid deforming the specimen
during the cutting and trimming process.
6.2.5 The soil specimen end surfaces shall be plane and perpendicular to the longitudinal axis
in accordance with ISO 17892-2. Grooves and holes in the ends and sides of the specimen should be
removed by further trimming or a new specimen selected if available. Otherwise, fill grooves or holes not
exceeding 1/6 of the specimen diameter with remoulded sample material. Grooves and holes in the ends
may be filled with a material that hardens with time and which does not release or absorb water.
10 © ISO 2018 – All rights reserved

ISO 17892-9:2018(E)
6.2.6 Undisturbed clay and clayey specimens that may swell in contact with water shall be prevented
from swelling caused by the specimen sucking water from the porous discs. The preferred method to
achieve this is to mount the specimen with dry porous discs and to flush them with water while applying
a vertical and horizontal stress high enough to inhibit swelling, but below the intended effective stress
required at the end of consolidation.
6.2.7 Specimens may be prepared in the laboratory by compacting the material in layers into a split
mould with or without the rubber membrane mounted inside. If water is mixed into the material, at
least 16 h should be allowed for the water to equalize over the whole soil mass, before compaction.
Under-compaction in layers may be used for sand to achieve a homogeneous specimen. Reconstituted
specimens of sand may also be prepared by pluvial compaction in air or under water.
6.2.8 Specimens of coarse grained material may be held together by applying a slight vacuum (typically
10 to 20 kPa) when the split mould is removed, until a positive cell pressure of equal magnitude has been
applied.
6.2.9 Measure the specimen height, diameter and mass in accordance with ISO 17892-2 by linear
measurement.
6.2.10 Check that the membrane to be used is free from damage that may cause leakage during the test.
6.2.11 Mount the specimen into the apparatus, with the filter papers (if used), membrane and O-rings
so that it is centred with respect to the top and bottom platens. Take extreme care to avoid, as much
as possible, deforming the specimen during the mounting process. Very soft specimens may have to be
mounted without touching the specimen by hand at any stage during the preparation.
6.2.12 Complete the assembly of the triaxial cell.
6.3 Saturation of specimen
6.3.1 Saturation
6.3.1.1 The porous discs and filter papers, the pore pressure measuring system and the specimen shall
be sufficiently saturated so that the measured pore pressure corresponds to an undrained soil condition
during undrained shearing, and that an accurate volume change is measured during drained shearing.
6.3.1.2 The cell pressure shall be raised in order to apply an effective stress to the specimen sufficient
to prevent swelling of the specimen, but lower than the intended effective stress required at the end of
consolidation.
6.3.1.3 If the specimen or the porous discs and filter papers are to be saturated (or flushed) with water
after mounting, de-aired water meeting the requirements of 5.9 shall be used.
6.3.1.4 Sand specimens may be flushed with carbon dioxide prior to flushing with water to speed
up the saturation process as carbon dioxide is much more soluble than air in water. A vo
...