Two conventional CD triaxial compression tests were conducted on a dense angular dry sand at the same void ratio. Test A had a confining pressure of 150 kPa, while in test B the confining pressure was 600 kPa; these stresses were held constant throughout the test. At failure, tests A and B had maximum principal stress differences of 600 and 2550 kPa, respectively.

(a) Plot the Mohr circles for both tests at initial conditions and at failure..

(b) Assuming c = 0, determine ψ.

(c) What is the shear stress on the failure plane at failure for both tests?

(d) Determine the theoretical orientation of the failure plane in each specimen.

(e) What is the orientation of the plane of maximum obliquity?