A 10 ft layer of normally consolidated saturated clay is found at depth of 20 ft beneath a formation of partially saturated sandy silt with unit weight of 115 lb/ft cubed. Void ratio of the clay is 1.5 and specific gravity is 2.6. Find the change in thickness of the clay that will occur if the load on the surface increases by 2 tons/ft squared? The clay rests on sounds unweathered rock. Coefficient of consolidation of the clay is 4 ft squared/month. How many months will it take to have the clay settle 3 inches?