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The soil profile at a site consists of a clay layer 10 m thick,sandwich between two sand layers. The top sand layer has a densityof 1.9 Mg/m³ and is 5 m thick. Below this layer is a 10m thick clay layer with a saturated density of 1.8 Mg/m³and a saturated water content 42%. The deeper sand layer has asaturated density of 1.9 Mg/m³ and extend to the depthinvestigated at the site. The water table was detected at the topof the clay layer.

         Theresults of a consolidation test performed on a sample recoveredfrom the mid point of the clay layer indicated the followingproperties for the clay:

1. Effective pre-consolidation pressure of 130 kPa;
2. Compression index C_c = 0.40;
3. Re-compression index C_r = 0.03; and
4. Consolidation coefficient C_v = 0.544 *10^-2 cm²/sec.

The site is being proposed to begraded by compacting an additional layer.

The new compacted layer will impose a total stress increment of75 kPa on the present ground surface. It is desired to obtain thefollowing information:

1. Estimate the ultimate consolidation settlement due tograding;
2. Estimate the time in weeks that it will take to reach theaverage degree of consolidation U_ave= 90%; and
3. At the time calculated in 2.), estimate the excess porepressure still present at the mid-point of the clay layer.