Effects of Lateral Loads on a Single Pile

Abstract

Design of piles under lateral loads requires estimation of ultimate load carrying capacity of the pile and also, the pile deflections need to be evaluated to determine the allowable loads. For estimating the pile response, structural engineers invariably utilize the simplified method prescribed in the Indian code IS 2911-2002 (Indian Standard Code of Practice for Design of Pile Foundations, 2002). The method is based on replacing the pile soil system by an equivalent cantilever, the length of which is a function of subgrade reaction of the surrounding soil and the pile geometry. However, the method described is applicable only for flexible piles, where the maximum depth coefficient L/T is equal to or exceeds 4.0. To estimate the pile response for rigid piles, simplified procedures are not suggested and hence in the present study, an attempt has been made to evaluate the pile response under lateral loads using detailed soil–pile analysis. Parametric studies are carried out for various pile lengths and various soil stiffness. The pile responses thus obtained are compared with the method given in IS 2911-2002. It was observed that the pile response based on IS 2911-2002 compared reasonably well with the detailed soil–pile model even for L/T ≥ 2.5. However IS 2911-2002 underestimates the pile head deflections for L/T < 2.5 for both free headed and fixed head piles and hence detailed soil–pile analysis is essential for such situations. The variation of pile response with soil stiffness is also evaluated using these methods and the results are presented. The soil–pile analysis is carried out using subgrade modulus approach. The soil stiffness is assumed to vary linearly along the pile depth and hence the study is applicable for cohesionless soils which can be used for practical design of single pile subjected to lateral loads.