3 30 points A sandy soil has a 35 In a drained triaxial tes

3. (30 points) A sandy soil has a = 35°. In a drained triaxial test on the same soil, the deviator stress at failure is 5.38 ksf. What is the chamber confining pressure?

Solution

Solution:-

Given

Deviator stress at failure = (sigma)_d = 5.38 ksf

(phi)’ = 35 degree

Chamber confining pressure = (sigma)₃

_(sigma)1 = (sigma)₃ + deviator stress at failure

_(sigma)1 = (sigma)₃ + 5.38

We know that

Sin(phi)\' = (sigma₁ – sigma₃)/(sigma₁ + sigma₃)

Sin35 = (sigma₃ + 5.38 – sigma₃)/(sigma₃ + 5.38 + sigma₃)

(sigma)₃ = 2.004 ksf   

Chamber confining pressure(sigma₃) = 2.004 ksf     Answer