Bearing Capacity of Skirted Ring Footing Resting on Dense Sand Overlying Soft Clay

Abstract

This study determines the ultimate bearing capacity of unskirted/skirted ring footing on dense sand of finite thickness on top of a layer of indefinite extent of soft clay under concentric vertical stress by means of finite element analysis. The thickness of an upper dense sand layer varied between 1 and 4 metres. The upper dense sand layers maintained a friction angle between 40° and 44°. The results indicate that the bearing capacity of footings C, R, IS, OS, and DS increases as the thickness (H) of the upper dense layer increases. Cohesion of the lower soft clay layer increases the bearing capacity of the C, R, IS, OS, and DS footings for a given thickness of the upper dense sand layer. As the friction angle of the upper dense sand layer increases, the bearing capacity of footings C, R, IS, OS, and DS varies little. At a thickness of 1 m for the upper dense sand layer, the footing with the highest bearing capacity was DS, followed by IS, OS, C, and R. At an upper dense sand layer thickness of 2 m or 4 m, the bearing capacities of footings DS, C, R, and IS was greater than those of footing OS, whereas the bearing capacities of footings C, R, and IS was comparable at the same thickness. The displacement contours validate the computational study's findings. Adding an inner skirt and double skirt is more effective at reducing the tendency of dense sand to escape through the ring annulus than adding the outer skirt.