A 600 mm diameter pile is installed up to the bottom of a 16 m thick stiff clayey soil. The pile rests on dense gravelly strata. The average undrained shear strength of the clay is 60 kPa (ou = 0) and its saturated unit weight is 18 kN/m. If the pile has an enlarged base of diameter 1-2 m, determine its ultimate uplift capacity. Assume that the groundwater level is at the ground surface. Ignore the benefit due to the weight of the pile. Take adhesion factor a = 0.8 and friction coefficient in uplift K = 0.5.