two triaxial compression tests were performed on two prepared samples of the same limestone. At a confining pressure of 2000 psi, the first sample failed at 9000 psi. Then at a confining pressure of 5000 psi, the other sample failed at 21000 psi. (a) plot the 2 test results on a shear stress-nomal stress diagram and draw in the Mohr envelope. (b)determine the slope angle of the Mohr envelope. (c) what is the 'So' value? (shear strength or cohesion) (d) what was the shear stress on the failure plane at failure for both tests?