EVOLUTIONARY-BASED PREDICTION OF ε50 FOR THE LATERAL LOAD-DISPLACEMENT BEHAVIOR OF PILES IN CLAY

Analyzing piles that are subjected to lateral loads reveals that their behavior depends on the soil's resistance at any point along the pile as a function of the pile's deflection, known as the p-y curve. On the other hand, the deformation characteristics of soil defined as "the soil strain at 50% of maximum deviatoric stress (epsilon(50))" have a considerable effect on the generated p-y curve. In this research, several models are proposed to predict epsilon(50) specifically for designing the very long pile foundations of offshore oil and gas platforms in the South Pars field, Persian Gulf, Iran. Herein, epsilon(50) is evaluated using extensive soil data, including in-situ and laboratory test results using evolutionary polynomial regression (EPR). The effects of the undrained shear strength, the normalized tip resistance of the cone penetration test, the over-burden pressure, the plasticity index and the over-consolidation ratio on epsilon(50) are investigated in marine clays. It is demonstrated that the normalized cone tip resistance, which is an indication of the soil's undrained shear strength, leads to more realistic epsilon(50) values compared with the laboratory-derived undrained shear strength parameter. In addition, the application of the soil-index properties and the over-burden pressure in the models, improves their estimation quality. Furthermore, the results of full-scale lateral pile load tests at different sites are used in order to validate the performance of the proposed models when it comes to predicting the behavior of the lateral piles.