Two CU triaxial tests are performed on a clay specimen. At failure, the results are: Test 1: σ3 = 30 kPa, P = 0.45 kN, Area of specimen = 0.01 m2 , u = 10 kPa Test 2: σ3 = 60 kPa, P = 0.70 kN, Area of specimen = 0.01 m2 , u = 20 kPa a) Find σ1, σ3, σ'1, and σ'3 at failure for both tests. b) Draw the effective stress Mohr's circle for both tests and draw the Mohr-Coulomb failure envelope for the clay. What are ' and c' for the clay? Write the equation for the MohrCoulomb failure envelope.