Uplift Capacity of Pile Groups in Sand


Nihar Ranjan Patra

Lecturer, Department of Civil Engineering,
Indian Institute of Technology Kanpur, U.P., India


Prabhakar Jagannath Pise

Professor, Dept of Civil Engineering,
Indian Institute of Technology Kharagpur, India


Experimental investigations on model pile groups of configuration (2x1, 3x1, 2x2, 3x2) along with a single pile subjected to uplift loads were conducted in dry dense sand. The embedment length to diameter ratios of L/d=12 and 38, center to center spacing of piles in the groups 3d, 4.5d and 6d and two surface characteristics were used. The load-displacement response, ultimate resistance and the variation of group efficiency with the spacing and number of piles in a group have been studied. The efficiency of a pile group increases with an increase in the spacing. For rough groups it decreases with increase in length of piles. A simplified method has been proposed to predict the ultimate uplift capacity of a pile group. The method takes into consideration of the embedment length to diameter ratio, spacing of piles in a group, its configuration, soil-pile friction angle and soil properties. A comparison of the predicted values of the ultimate resistance by the simplified analysis with the writers’ experimental values, and, also with those reported by others, showed reasonably good agreement.

Keywords: Pile groups, Axial uplift loads, ultimate uplift capacity, foundations, sandy soil


Get the entire paper