Semi-numerical analysis of negative skin friction on permeable pile due to consolidation induced by piling

A semi-numerical approach is proposed to estimate the dissipation of excess pore water pressure and the development of negative skin friction at the normal impervious pile and the permeable pile after piling. An impeded drainage boundary associated with the opening ratio and opening size is introduced to simulate the drainage condition at the soil-permeable pile interface. In the proposed mathematical framework, analytical approaches are adopted to solve the linear equations, and numerical techniques are utilized to address the nonlinear problems so that the adaptivity and efficiency of the mathematical framework can be well balanced. Through comparisons with the field tests, the model tests, and the theoretical answers, the correctness and rationality of the proposed method are validated. Through a parametric study, the key design parameters of the permeable pile are investigated, and the following design tips are obtained: 1. The opening ratio plays the most important role in the drainage efficiency of the permeable pile; 2. Increasing the number of openings is preferred rather than increasing the size of openings, especially when the opening ratio is determined.