🏗️ Consolidated triaxial compression test on fully water-saturated soil specimens — cylindrical specimen (undisturbed, recompacted, remoulded or reconstituted) consolidated isotropically or anisotropically under drained conditions and then sheared undrained (CIU, CAU, with pore pressure measurement) or drained (CID, CAD); shear strength, stress–strain relationship, effective stress paths; strength parameters from at least three related tests, PN-EN ISO 17892-9

Construction PN-EN ISO 17892-9

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 17892-9:2018-05 (Polish version), in full (our translation): “This document specifies a method for consolidated triaxial compression tests on fully water-saturated specimens. This document applies to the laboratory determination of shear strength during compression of specimens within geotechnical investigations. The cylindrical specimen, comprising undisturbed, recompacted or reconstituted soil, is subjected to isotropic or anisotropic stress under drained conditions and then sheared under undrained or drained conditions. The test allows the determination of shear strength, stress–strain characteristics and effective stress paths. All stresses and strains are denoted as positive values in compression. NOTE 1 This document describes a test on a single specimen. To determine the strength parameters, a series of tests on at least three related specimens is required. Procedures for evaluating the test results are presented in Annex B. In addition, where required, the strength parameters are given in the test report. Special procedures such as: a) tests with lubricated ends; b) multi-stage tests; c) tests with zero lateral strain (K0) during consolidation; d) tests with local strain measurement or pore water pressure tests; e) tests without rubber membranes; f) “extension” tests; g) shearing under varying cell pressure conditions; are not fully covered by this procedure. Nevertheless, these special tests can refer to the general procedures described in this document. NOTE 2 This document fulfils the requirements for consolidated triaxial compression tests within geotechnical investigations according to EN 1997-1 and EN 1997-2.” (In the ISO text the list of soils also includes remoulded soil.) We read the text of the standard in the preview of ISO 17892-9:2018 from the cover to 5.1 with Figure 1 (diagram of the apparatus); we do not have the rest of Clause 5, Clauses 6–8 or Annexes A and B.

ACCORDING TO THE TEXT OF ISO 17892-9:2018 (foreword, introduction, Clauses 1–5.1). The standard was prepared by CEN/TC 341 together with ISO/TC 182 (Vienna Agreement); the first edition replaces ISO/TS 17892-9:2004 after technical revision and incorporates Cor.1:2006. Scope (1) — as on the card. References (2): ISO 14688-1, ISO 17892-1, -2 and -3. Definitions (3): CIU — isotropically consolidated undrained; CAU — anisotropically consolidated undrained; CID — isotropically consolidated drained; CAD — anisotropically consolidated drained; pore pressure — pressure of water in the voids of the specimen; back pressure — external pressure increasing the pore pressure before consolidation or shearing to ensure saturation; cell pressure — pressure of the cell fluid; deviator stress — difference between vertical and horizontal total stress; effective stress — difference between total stress and pore pressure; failure — the condition at which one of the criteria is met: peak deviator stress, peak ratio of vertical to horizontal effective stress, a specified strain criterion (e.g. 10 % vertical strain) or another definition if required. Symbols (4): among others B — pore pressure coefficient (increase of pore pressure caused by an increase of cell pressure under undrained conditions), t₅₀ and t₁₀₀ (time for 50 % and 100 % primary consolidation), uB (back pressure at the start of shearing), vmax (rate of displacement of the load frame during shearing), εvf (expected strain at failure), corrections of stresses for membrane and filter paper; effective stresses are marked with a prime, directions with suffixes v and h. Apparatus (5.1): regular calibration, maintenance and checks according to Annex A; Figure 1 — load measuring device (alternative positions), air bleed, vertical displacement device, piston, top cap, O-rings, porous disc, specimen, membrane (with or without side drains), pedestal, control and measurement of cell pressure, cell, drainage tubes, pore pressure sensor, volume change measurement, control and measurement of back pressure, flushing system. From the table of contents (in part): isotropic consolidation (CIU and CID, 6.4) and anisotropic consolidation (CAU and CAD, 6.5), undrained shearing (6.7.2) and drained shearing (6.7.3), Annex B — additional calculations of effective shear strength.

STATUS (PKN catalogue cards as of 02.10.2026). The card of PN-EN ISO 17892-9:2018-05 (Polish version, published 01-10-2020, 32 pages, price group P) has no “Withdrawn” header: Building and Construction Sector, KT 254 Geotechnics, ICS 13.080.20 and 93.020, “Introduces: EN ISO 17892-9:2018 [IDT], ISO 17892-9:2018 [IDT]”. The PKN search for “PN-EN ISO 17892-9” (02.10.2026) shows the English and Polish versions 2018-05. The EVS catalogue (read 02.10.2026) lists ISO 17892-9:2018 as valid from 28.02.2018.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 02.10.2026). The number 17892-9 appears in 9 records at 6 laboratories: AB 283, AB 962, AB 1416, AB 1770, AB 1778, AB 1914. In the current scopes on the PCA website (read 02.10.2026, issues from 24.09.2024 to 17.07.2026) all give “PN-EN ISO 17892-9:2018-05”. The “Laboratories” tab searches for entries STARTING WITH “PN-EN ISO 17892-9” and shows all 6 laboratories — checked with the tab query on the production server labcoda.pl on 02.10.2026.

WHAT THE LABORATORIES TEST (PCA entries). Soils — “Tests of soils in the triaxial compression apparatus after saturation with water”, cell pressure from 0 to 3500 kPa (AB 962, AB 1416); “Shear strength, consolidated triaxial compression test method on fully water-saturated specimens (CU and CD)” (AB 1770, two entries); “Determination of strength parameters under effective and total stress conditions, consolidated triaxial compression test method on fully saturated specimens” (AB 283); “Angle of friction” and “Cohesion”, load range from 0 to 25 kN, “shearing method in the triaxial compression apparatus” (AB 1778); “Compressive strength”, cell pressure from 0 to 3000 kPa, “consolidated undrained (CU)” (AB 1914 — undrained variant only).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Saturation: the standard concerns fully saturated specimens — according to definition 3.6 saturation is ensured by back pressure, and Clause 4 defines the pore pressure coefficient B; the part we read contains no saturation criteria. Number of tests: one specimen gives one point — the angle of friction and cohesion (given e.g. by AB 1778) require at least three related tests and evaluation according to Annex B. Definition of failure: peak deviator stress, peak effective stress ratio and 10 % strain may give different strength values, so a result without a named criterion is ambiguous (we do not have the reporting requirements). Type of test: CU (undrained, with pore pressure measurement) and CD (drained) are different tests with different results; AB 1914 has only CU in its scope. Signs: compressive stresses and strains are positive. Special procedures: multi-stage tests, K₀ consolidation, local strain measurement, tests without membranes, extension tests or tests with varying cell pressure are not fully covered by the standard.

WHAT WE DO NOT STATE. We do not have 5.2–8 or Annexes A and B: requirements for the cell, membranes, transducers and shearing rate, saturation criteria (B values), consolidation time, formulae for membrane and filter paper corrections, formulae for stresses and strains or the method of determining strength parameters — we therefore give none of these figures.

Method principle

A cylindrical soil specimen in a membrane is saturated (back pressure), consolidated in the triaxial cell under isotropic or anisotropic stress with drainage, and then sheared axially undrained with pore pressure measurement (CIU, CAU) or drained with volume change measurement (CID, CAD), to failure according to the adopted criterion.

Applications

• Soils in geotechnical investigation — effective strength parameters (angle of friction, cohesion); 6 laboratories in PCA scopes
• Design of foundations, slopes and retaining structures according to EN 1997-1 and EN 1997-2
• Effective stress paths and stress–strain relationships of saturated soils

Key parameters

Standard

Standard number

PN-EN ISO 17892-9:2018-05 (wersja polska; EN ISO 17892-9:2018 IDT, ISO 17892-9:2018 IDT)

Title (PL)

Rozpoznanie i badania geotechniczne — Badania laboratoryjne gruntów — Część 9: Ściskanie trójosiowe z konsolidacją na próbkach całkowicie nasyconych wodą

Title (EN)

Geotechnical investigation and testing — Laboratory testing of soil — Part 9: Consolidated triaxial compression tests on water saturated soils

Step-by-step procedure

1. Specimen

   Cylinder of undisturbed, recompacted, remoulded or reconstituted soil in a membrane; water content and density according to ISO 17892-1 and -2. PN-EN ISO 17892-9:2018-05 current (PKN cards as of 02.10.2026).

2. Saturation

   Back pressure increases the pore pressure to ensure saturation (3.6); coefficient B is defined in Clause 4 — saturation criteria outside the part we read.

3. Consolidation

   Isotropic (CIU, CID) or anisotropic (CAU, CAD) with drainage; t₅₀ and t₁₀₀ from the consolidation curve (6.4, 6.5).

4. Shearing

   Undrained with pore pressure measurement (CIU, CAU) or drained with volume change measurement (CID, CAD), to failure according to the adopted criterion (6.7).

5. Results

   Deviator stress, effective stresses, stress paths; strength parameters from at least three tests according to Annex B (we do not have the formulae).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard contains no safety warnings in the part we read; the cell operates under pressure — safety rules are set by the laboratory
• TECHNICAL NOTE: strength parameters require at least three related tests; with the result, name the adopted failure criterion and the type of test (CU/CD, I/A)

Frequently asked questions