Reduction Factors for Laterally Loaded Pile Groups Accounting for Pile Cross Sections and Soil Properties

P-y analysis approach is among the most widely used methods implemented for simulating the pile behavior under lateral loading. To obtain the p-y curve of a pile group, that of a single pile should be modified by a group reduction factor which is conventionally determined by the pile spacing to diameter ratio and the pile row number in the group. The pile section types and soil characteristics i.e. internal friction angle are among other important factors affecting the group reduction factor. However, the influence of these parameters has not been investigated in previous researches, thoroughly. In this study, continuum models of eight pile groups with different conditions regarding pile section types and soil properties were built and analyzed. It was found that the group reduction factor of the pile group with square tube section is less than that of the group of piles with pipe sections, due to group effects. On the other hand, for the pile groups of both section types, the greater internal friction angle, increases the shadowing and edge effects which results in lower group reduction factor. Moreover, the group reduction factors calculated based on numerical modeling results were compared with the recommendations of AASHTO and FEMA guidelines. It was also shown that the continuum model results conform with the results of experimental studies.