Question

Q3. Vane shear tests were conducted in layer of soft clay. The vane dimensions were 63.5 mm (D)x 127 mm (H). At a certain depth, the torque required to cause a failure was 0.051 kN.m. The liquid limit of the clay was 56 and the plastic limit was 23. Estimate the undrained cohesion, c of the clay for use in the design by applying Bjerrum's λ relationship given below. Investigate about what is Bjerrum's relationship: 1.7-0.54 log[PI(%)] Discuss when you would use vane shear tests for determining the undrained shear strength tests instead of conventional unconfined compression tests. Typically, which one of the tests, SPT or CPT is used for determining the in-situ shear strength of soft clays? Give reasons.

Answer 1

, d=615 mm, h-127 mm, WL 56% , W,-23% If w-wp -56-23-33% = 0,281 Now, Sheas stt h= Undeure & Cohesion (a) 4) 2 o, o54 N/mm2 day sampling sk handling os t can be