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Option 3 : Shear strength parameters
Concept:
Triaxial test is used to determine the shear strength parameter of soil.
The triaxial compression test consists of two stages:
First stage: In this, a soil sample is set in the triaxial cell, and confining pressure is then applied.
Second stage: In this, additional axial stress (also called deviator stress) is applied which induces shear stresses in the sample. The axial stress is continuously increased until the sample fails.
During both the stages, the applied stresses, axial strain, and pore water pressure or change in sample volume can be measured.
S = C̅ + σ tan ϕ
Where,
S = Shear strength of soil, C = Cohesion of soil, and ϕ = angle of internal friction
C & ϕ are known as Shear strength parameter of soil.
Tests carried out to measure the shear strength of the soil:
i) Direct shear test
ii) Unconfined compression test
iii) Triaxial compression test
iv) Vane shear test