IS 2720:1986 Part 15 is the Indian Standard (BIS) for methods of test for soils - determination of consolidation properties. This part of IS 2720 specifies the test procedure for determining the consolidation properties of cohesive soils under one-dimensional loading. It provides methods for evaluating the magnitude and rate of consolidation, which are essential for predicting foundation settlement.
Describes the procedure for conducting one-dimensional consolidation (oedometer) tests to determine the compressibility and consolidation characteristics of soils.
Overview
- Status
- Current
- Usage level
- Frequently Used
- Domain
- Geotechnical — Soil and Foundation
- Type
- Testing Method
Also on InfraLens for IS 2720
Practical Notes
! Always ensure porous stones are properly saturated before the test to prevent them from absorbing moisture from the soil specimen.
! Careful sample extraction into the consolidation ring is critical; sample disturbance significantly alters the preconsolidation pressure and compression index.
! Maintain a relatively constant room temperature during the test, as temperature variations affect water viscosity and thereby the rate of consolidation.
Frequently referenced clauses
soilcohesive soilclaysilt
International Equivalents
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Key Values5
Quick Reference Values
Minimum specimen diameter60 mm
Minimum specimen thickness20 mm
Minimum diameter to thickness ratio3
Standard load duration per increment24 hours
Standard load increment ratio (Δp/p)1.0
Key Formulas
Cv = (Tv * d^2) / t — Coefficient of consolidation (where d is drainage path)
Cc = (e1 - e2) / log10(p2/p1) — Compression Index
mv = (e1 - e2) / ((1 + e1) * (p2 - p1)) — Coefficient of volume compressibility
av = (e1 - e2) / (p2 - p1) — Coefficient of compressibility
Tables & Referenced Sections
Key Clauses
Clause 3 - Equipment
Clause 4 - Preparation of Specimen
Clause 5 - Procedure
Clause 6 - Calculations
Clause 7 - Report
Frequently Asked Questions3
What is the standard load increment sequence?+
Typically, the load is doubled at each stage (e.g., 25, 50, 100, 200, 400, 800 kN/m2), resulting in a load increment ratio of 1.
How is the coefficient of consolidation (Cv) calculated from test data?+
It is determined graphically using either the logarithm of time fitting method (Casagrande) or the square root of time fitting method (Taylor).
How long should each pressure increment be applied?+
Generally for 24 hours, or until primary consolidation is observed to be complete via dial gauge readings.
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