A rising water table within the soil increases pore pressure (and buoyancy), so effective stress decreases. (If the water table is already above ground, a further rise does not change it.)
Question 50Easy
In a triaxial test, the intermediate principal stress is:
The two horizontal stresses are both the cell pressure, so σ₂ = σ₃ (the minor principal stress).
Question 54Easy
In a direct shear test, the shear stress and normal stress on a dry sand at failure are 0.6 kg/cm² and 1 kg/cm² respectively. The angle of internal friction of the sand will be nearly:
Dry sand: c = 0, so \(\tan\phi = \tau/\sigma = 0.6/1 = 0.6\) and \(\phi = \tan^{-1}0.6 \approx 31^\circ\).
Question 55Medium
The static cone penetration test and the standard penetration test are performed on a soil at a certain depth. The value of static cone resistance is 8 MPa and the N value is 20. The soil met at that depth is: