Chapter 12, Problem 12.10P

### Principles of Geotechnical Enginee...

9th Edition
Braja M. Das + 1 other
ISBN: 9781305970939

Chapter
Section

### Principles of Geotechnical Enginee...

9th Edition
Braja M. Das + 1 other
ISBN: 9781305970939
Textbook Problem

# A drained triaxial test was conducted on a normally consolidated clay specimen with a chamber confining pressure of 145 kN/m2. At failure, the deviator stress was 198 kN/m2. Determine the soil friction angle, ϕ ′ .

To determine

Find the soil friction angle ϕ.

Explanation

Given information:

The confining pressure (σ3) is 145kN/m2.

The deviator stress at failure (Δσd)f is 198kN/m2.

Calculation:

Calculate the major principal effective stress at failure using the formula:

σ1=σ3+Δσd

Here, σ1 is major principal effective stress and (Δσd)f is the deviator stress at failure.

Substitute 145kN/m2 for σ3 and 198kN/m2 for (Δσd)f.

σ1=145+198=343kN/m2

Show the expression of major effective principal stress as shown below:

σ1=σ3tan2(45+ϕ2)+2c(45+ϕ2)

Here, σ3 and σ1 minor and major effective principal stress and c is cohesion

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