two isotropically consolidated undrained (ciu) triaxial tests, CU1 triaxial tests, CU1 and CU2, were conducted on a normally consolidated (Nc) clay under effective consolidation stresses of 100 and 200 kPa respectively. The undrained shear strength obtained from a DSS test on a sample taken from point A was 18 kpa. Poin A was 5m below the ground surface, as shown in FIGURE q2. An oedometer test was also carried out on the sample taken from Point A. From the test, the OCR, compression index and recompression index were determined as 4, 1.2 and 0.3 respectively. The ground water level (GWL) was the same as the ground surface
(a) calculate the Cu/ σv0 value at point A
(b)estimate the Cu value at point B which was 10 m below the ground surface and the OCR value at this point was 1.
(c)a 5m high sand fill with a unit weight of 20 kn/m3 was subsequently placed over a large extent on to the clay layer. estimate the Cu value at points A and B after the clay layer is fully consolidated, assuming the Cu/ σv0' ratio remains the same.
(d) discuss brefly how the undrained shear strength is affected by (i) the effective overburden stress and (ii) the OCR of soil.