Retaining wall problem example 5

A rigid retaining wall 19.69 ft high has a saturated backfill of soft clay soil. The properties of the clay soil are ysat = 111.76 lb/ft3, and unit cohesion cu = 376 lb/ft2. Determine (a) the expected depth of the tensile crack in the soil (b) the active earth pressure before the occurrence of the tensile crack, and (c) the active pressure after the occurrence of the tensile crack. Neglect the effect of water that may collect in the crack.