IS 2720:1981 Part 12 is the Indian Standard (BIS) for methods of test for soils - part 12: determination of shear strength parameters of soil by triaxial compression test (undrained conditions). This standard prescribes the method to determine the shear strength parameters (cohesion and angle of shearing resistance) of soil using the triaxial compression test under unconsolidated undrained (UU) conditions. It is primarily used to evaluate the short-term stability of cohesive soils under rapid loading conditions.
Covers the determination of shear strength parameters of soil under undrained conditions using the triaxial compression test.
Overview
- Status
- Current
- Usage level
- Specialized
- Domain
- Geotechnical — Testing Methods and Quality Control
- Type
- Testing Method
Also on InfraLens for IS 2720
Practical Notes
! Always check rubber membranes for pinhole leaks before conducting the test to prevent premature drainage or failure.
! Undrained tests (UU) are fast and do not allow pore water dissipation, making them ideal for assessing short-term, end-of-construction stability in clays.
! Ensure the specimen ends are perfectly flat and perpendicular to the axis to avoid eccentric loading and uneven stress distribution.
Frequently referenced clauses
soilclaycohesive soil
International Equivalents
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Key Values4
Quick Reference Values
Length to diameter (L/D) ratio2.0 to 2.5
Minimum specimen diameter38 mm
Maximum particle size1/5th to 1/6th of specimen diameter
Standard rate of strain (plastic failure)1 to 2 percent per minute
Key Formulas
Axial strain (ε) = ΔL / L0
Corrected Area (A) = A0 / (1 - ε)
Deviator Stress (σ1 - σ3) = Axial Load / Corrected Area (A)
Major Principal Stress (σ1) = Deviator Stress + Confining Pressure (σ3)
Tables & Referenced Sections
Key Clauses
Clause 4 - Apparatus
Clause 5 - Preparation of Test Specimens
Clause 6 - Procedure for Unconsolidated Undrained Test
Clause 7 - Calculations and Report
Frequently Asked Questions4
What is the recommended length-to-diameter ratio for the test specimen?+
The length should be 2 to 2.5 times the diameter of the specimen.
How is the corrected cross-sectional area of the specimen calculated?+
Corrected Area A = A0 / (1 - ε), where A0 is the initial area and ε is the axial strain.
What is the minimum allowed diameter for a triaxial soil specimen?+
38 mm.
When is an Unconsolidated Undrained (UU) test used?+
It is used to determine the undrained shear strength (Su) of cohesive soils for short-term stability problems like immediate post-construction scenarios.
QA/QC Inspection Templates
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