Test $B$ is a direct shear test. The normal stress of $50$kPa is held constant during the test. The initial horizontal stress is $25$kPa. At failure, the normal stress is still $60$kPa and the shear stress is $45$kPa.

You are asked to determine:

a$)$ Principal stresses at failure.

b$)$ Orientation of the failure plane.

c$)$ Orientation of the major principal plane at failure.

d$)$ Maximum shear stress at failure and the angle of the plane on which acts.

Calculate the available shear strength on this plane and the factor of

safety on this plane.