Pile-soil-pile interaction in pile groups under lateral loading

This paper describes the results of a numerical analysis of single pile and pile groups subjected to monotonous lateral loading using ABAQUS finite element program. The variables investigated in this study includes embedded pile cap, pile diameter, pile length, and pile spacing. The 1 x 3 pile group was selected to investigate the lateral resistance of the group and distribution of the resistance among the piles distribution and the influence of the trailing piles on the lateral resistance of the leading pile. The piles and caps were concrete and the soil followed Cam-clay constitutive model.; The p-y method has been widely used to design the lateral capacity of the piles. To accommodate the contribution of the pile cap on the lateral capacity of the pile, methods based on the soil lateral modulus of subgrade reaction or the Rankine passive resistance have been used in the design. For lateral capacity of pile group, each pile in the group is given a multiplying factor. The factor is the ratio between the lateral capacity of a pile in the group to the capacity of a single pile. A factor of less than 1.0 has been used for the design of individual piles in the group.; The results of this study show that for a single pile, the present of the cap not only affects the lateral capacity of the pile but the location of the point of application of the load also affects the response. When the cap is pushed laterally, vertical stress below the base of the front part of the cap is induced, increasing the confining pressure of soil in front of the pile, and this results in the increase of the lateral capacity. When the lateral load is applied on the front of the cap, the lateral capacity drops due to reduction in the induced vertical stress in the front of the pile.; For the piles in the group, the results show that the leading pile has a higher resistance than the trailing piles as expected. However, this study also shows that the leading pile has a higher lateral capacity than the capacity of the single pile. This indicates that the multiplying factor of less than 1.0 as usually used for the leading pile is conservative. Further observation on soil elements around the side of the leading pile show higher horizontal stress than the soil elements on the trailing piles at same location.; The general trend of this phenomenon is similar in short and long piles. In the group with larger pile spacing, the difference in the capacity between the leading pile and the trailing pile decreases.