The behavior of laterally loaded single piles and group piles in sand

The finite element method, along with an elastic-plastic sand constitutive model, is used to investigate the response of laterally loaded single and group piles in sand. A single surface, isotropic hardening constitutive model with nonassociative flow rule is used to model the behavior of sand. The purpose of the study is to gain a better understanding of the soil and pile behavior of laterally loaded single and group piles using the finite element approach.; The accuracy of the non-linear finite element approach is verified by analyzing two full-scale pile load tests. Successful comparisons between predicted and measured pile and soil response are obtained. Effect of pile properties (pile stiffness and diameter) and soil properties (stiffness, shear strength, and volume change characteristics) on the pile and soil response of laterally loaded single piles are investigated. Results computed with finite element analyses are used to evaluate existing methods for predicting p-y response and ultimate soil resistance.; Effect of pile-soil-pile interaction (group interaction) is investigated by analyzing the effect of load on an in-line pile group. Lateral loads are applied both perpendicular and parallel to the line of piles. The effect of pile spacing on group interaction is also investigated. A substantial reduction in ultimate soil resistance for piles in a group relative to that of single piles is observed. Group effects are minimal for a pile spacing of 9 times the pile diameter (for piles along the direction of loading) and for a pile spacing of 6 times the pile diameter (for piles normal to the direction of loading).; A "modulus multiplier" method is developed as a means to account for group effects in piles. The method modifies p-y curves for a single pile to provide a p-y response for a pile within a group. Modulus multipliers are developed as a function of pile spacing and departure angle. A method for analysis of pile groups subjected to lateral loads is proposed. Two full-scale pile groups subjected to lateral loads in sand are analyzed using the proposed method, and a good agreement between predicted and measured pile response is obtained.