Q$4)(9\%)$:

A saturated clay layer is tested by a field vane that has a diameter of $9$ cm and height of $10$ cm $.$ A torque of $42$ Nm is required to shear the soil. The vane was then rotated to remould the soil completely. The torque required to continue this rotation decreased to $28$ Nm $.$

a$)(5\%)$ Calculate the undrained shear strength of this clay.

b$)(4\%)$ Calculate the residual shear strength and sensitivity of this clay.

$2$