A rectangular foundation, 10 2 m2, is to carry a total uniform pressure of 400 kPa and is to be founded at a depth of 1 m below the surface of a saturated sand of considerable thickness. The bulk unit weight of the sand is 18 kN/m3 and standard penetration tests carried out below the water table indicate that the deposit has an average N value of 15.If the water table occurs at the proposed foundation depth, determine a value for the settlement of the centre of the foundation. (Use De Beer and Martens method.)