Development of generalized pseudostatic p-y curves for liquefied sands

Based upon an increased need to understand the behavior of laterally loaded pile foundations in liquefied sands, small-scale and full-scale experiments have been conducted in the past including centrifuge, shake table and field tests. No work had been done to date on combining the results of the different experiments in a validation effort. Several p-y (soil resistance-pile displacement) models to account for liquefied soil behavior have been proposed including use of p-multipliers, Matlock's soft clay model, or neglecting lateral resistance from the soil totally. The p-multiplier and Matlock's soft clay model, which are more generalized for design purposes, show too much resistance at small displacements and not enough resistance at large displacements. Small-scale and full-scale test results have shown that these models fail to capture the true behavior of the soil in the liquefied domain or where the excess pore pressure ratios range from 20% to 100%. Finite element models have been developed to account for these behaviors, but these are quite complicated for design purposes and require a substantial amount of geotechnical investigation. As a result, a new generalized pseudostatic model has been developed for design purposes to capture these soil behaviors which takes into account readily available parameters for design including the sand's relative density in addition to the excess pore pressure ratio. This model has been developed and assessed against results obtained from 1-g shaking table, centrifuge, and full scale field tests. The new model includes an initial zone where the pile displaces without any soil resistance developing followed by soil dilation and increased soil resistance as the pile displaces beyond the initial zone. The concave upwards shape obtained matches the results obtained in the experiments previously conducted. A parametric analysis was performed for the new model which clearly showed the significant effect of the excess pore pressure ratio on the soil's resistance. Finally, a complete pseudostatic procedure has been recommended for design purposes.