A rock sample is placed in a strength-testing machine at atmospheric pressure and compressed axially to failure. A force of 12000 lbf was required for rock failure, and the cross-sectional area of the sample was 2.0 sq in. the sample failed along a plane that marks a 350 angle with the direction of compressional loading.
a) Construct the Mohr's circle using the two principal stresses present.
b) Compute the shear stress present along the plane of failure.
c) Compute the normal stress to the plane of failure.
d) Compute the angle of internal friction.
e) Compute the cohesive resistance of the material.
f) Label the parameters computed in the previous four steps on the Mohr's circle construction.
Using the Mohr criterion, compute the compressional force required for rock failure if the sample is placed under a 5000-psi confining pressure.