The profile at a site consists of 5 m of sand overlying 10 m of compressible clay, which in turn overlies a dense sand. The water table is at the top of the profile. The total unit weight of the top sand is 19 kN/m3, and that of the clay is 18 kN/m3. The cv of the clay is estimated to be 5 x 10-3 cm2/sec. Initially the clay is normally consolidated. It is planned to place a temporary fill that will exert a vertical load of 200 kPa over the entire site. How long must the fill be in place so that, after it is removed, the maximum past pressure at every point in the clay is at least 50 kPa larger than the vertical effective stress that existed before the fill was placed?

The profile at a site consists of 5 m of sand overlying 10 m of compressible clay, which in turn overlies a dense sand. The water table is at the top of the profile. The total unit weight of the top sand is 19 kN/m3, and that of the clay is 18 kN/m3. The cv of the clay is estimated to be 5 x 10-3 cm2/sec. Initially the clay is normally consolidated. It is planned to place a temporary fill that will exert a vertical load of 200 kPa over the entire site. How long must the fill be in place so that, after it is removed, the maximum past pressure at every point in the clay is at least 50 kPa larger than the vertical effective stress that existed before the fill was placed?