Assessment of the response of a laterally loaded pile group based on soil-pile interaction is presented in this paper. The behavior of a pile group in uniform and layered soil (sand and/or clay) is predicted based on the strain wedge (SW) model approach that has been developed to predict the response of a flexible pile under lateral loading. The pile group is characterized in terms of three-dimensional soil-pile interaction and then transformed into its one-dimensional beam on elastic foundation equivalent with associated parameters (modulus of sugrade reaction). Therefore, the interference among the piles in a group is determined based on the geometry of the mobilized passive wedge of soil in front of the pile in addition to the pile spacing. The overlap of shear zones among the piles in the group varies along the length of the pile and changes from one soil to another in the soil profile. Also, the interference among the piles grows with the increase in lateral loading. The modulus of subgrade reaction determined will account for the additional strains (i.e. stresses) in the adjacent soil due to pile interference within the group
