1. A type of rock is supposed to follow the Mohr-Coulomb linear strength criterion, the strength of the rock sample under uniaxial compression test is σc = 40 MPa, the angle between failure plane and the maximum principal stress σ1 is θ = 60o. If triaxial compression test is conducted on this rock sample with confining pressure σ3 = 3MPa, please calculate:
(a) The axial stress σ1 when the sample fails;
(b) The normal stress (σ) and shear stress (Τ) on the failure plane.