etical angle of the failure plane in the specimen.

A normally consolidated clay is placed in a triaxial test setup and it is consolidated under a cell pressure of 200 kPa; then, the specimen is sheared undrained in axial compression. The principal stress difference at failure is 150 kPa and the induced pore pressure at failure is125 kPa. It is desired to a) plot the total and effective stress Mohr circles; b) to the draw the effective stress failure envelope (assume that the effective cohesion is zero for a normally consolidated soil); c) determine the effective stress friction angle; and d) determine the theoretical angle of the failure plane in the specimen.