An elliptical artificial island has a major axis of 10km and minor axis of 7.5 km. A breakwater, 100m thick, forms the edges of the island. The area within the breakwater is to be filled with sand. The sand in its loosest state of porosity is 90% and the desired porosity when compacted is 20%. Assume the average thickness of completed island is 100m. Determine the quantity of the sand requured.

Refer to Problem 6.1. Using Eqs. (6.3) and (6.29), estimate the average stress increase (Δσav) below the center of the loaded area between depths of 3 m and 6 m. 6.1 A flexible circular area is subjected to a uniformly distributed load of 150kN/m2 (Figure 6.2). The diameter of the load area is 2 m. Determine the stress increase in a soil mass at points located 3 m below the loaded area at r = 0. 0.4 m, 0.8 m, and 1 m. Use Boussinesq’s solution. Figure 6.2 Increase in pressure under a uniformly loaded flexible circular area