Uplift Capacity of Pile Groups in Sand

 

Nihar Ranjan Patra

Lecturer, Department of Civil Engineering,
Indian Institute of Technology Kanpur, U.P., India
nrpatra@iitk.ac.in

and

Prabhakar Jagannath Pise

Professor, Dept of Civil Engineering,
Indian Institute of Technology Kharagpur, India
pjp@civil.iitkgp.ernet.in

ABSTRACT

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