Skempton pore pressure parameters A and B for a saturated soil under undrained loading relate excess pore pressure to principal stress increments as:
Choose the correct answer
Delta u = B [Delta sigma_3 + A(Delta sigma_1)]
Delta u = B [Delta sigma_3 + A(Delta sigma_1 - Delta sigma_3)]
Delta u = A x Delta sigma_1 + B x Delta sigma_3
Delta u = (Delta sigma_1 + Delta sigma_3) / 2
Correct Answer
B. Delta u = B [Delta sigma_3 + A(Delta sigma_1 - Delta sigma_3)]
Why is this the answer?
Skempton (1954): Delta_u = B[Delta_sigma_3 + A(Delta_sigma_1 - Delta_sigma_3)], where B = 1 for saturated soil (degree of saturation > 95%), A at failure: A = 0 to 0.5 for heavily OC clays; A = 0.5 to 1.0 for NC clays; A > 1.0 for very sensitive or loose sands. Negative A (OC clay) indicates tendency to dilate. Used in undrained triaxial analysis.
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