Precast driven piles are extensively used for infrastructure on soft soils, but the buildup of excess pore water pressure associated with pile driving is a challenging issue. The process of soil consolidation could take several months. Measures are sought to shorten the drainage path in the ground, and permeable pipe pile is a concept that involves drainage channels at the peak pore pressure locations around the pile circumference. Centrifuge tests were conducted to understand the responses of permeable pipe pile treated ground, experiencing the whole pile driving, soil consolidating, and axially loading process. Results show that the dissipation rate of pore pressures can be improved, especially at a greater depth or at a shorter distance from the pile, since the local hydraulic gradient was higher. Less significant buildup of pore pressures can be anticipated with the use of permeable pipe pile. For this, the bearing capacity of composite foundation with permeable pipe pile can be increased by over 36.9%, compared to the case with normal pipe pile at a specific time period. All these demonstrate the ability of permeable pipe pile in accelerating the consolidation process, mobilizing the bearing capacity of treated ground at an early stage, and minimizing the set-up effect. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Permeable pipe pile, a novel pile foundation integrating drainage and bearing functions, improves the bearing capacity of the pile foundation by accelerating the consolidation of the soil around the pile. In this study, a mathematical model is established to simulate the consolidation of surrounding clayey soils and the pile-soil interaction, where the rheological properties of the soils are described with the fractional derivative-based Merchant model, and the impeded drainage boundary is used to simulate the pile-soil interfacial drainage boundary. Corresponding solutions for pile-soil relative displacement, skin friction, and axial force on the pile shaft are derived by means of semi-analytical methods, and they are validated by comparing with experimental results and numerical simulation results. Based on the proposed semi-analytical model, a series of parametric analyses are conducted to investigate the influences of fractional orders, viscosity coefficients, pile-soil interface parameters, and pile-head loads on the pile-soil interaction characteristics. It is observed that during the transition stage, the axial force increases linearly with depth in the plastic segment, and then increases nonlinearly in the elastic segment until it decreases after reaching the neutral plane. In the elastic segment, the axial force on the pile shaft for a given time increases with the increases in the fractional order or the pile-soil interface parameter, but decreases with the increase of viscosity coefficient.

Permeable pipe piles accelerate the bearing capacity of the pile foundation by releasing the excess pore water pressure (EPWP) of the soil around the pile through appropriate openings in the pile body. This study couples the Material Point Method (MPM) and the Finite Element Method (FEM) to establish a full-process model of pile driving and consolidation of permeable piles, and proposes a continuous drainage boundary condition that can reflect the plugging effect of permeable holes. The correctness of the model and boundary conditions are verified by comparison with experiments, and then the effects of soil properties, opening characteristics, and boundary permeability on the accelerated consolidation effect of permeable piles are analyzed. The results show that: the permeable pile with a permeable area ratio greater than 50% and a local opening ratio greater than 5% can save more than 60% of the consolidation time compared to conventional piles; the proposed boundary conditions can accurately describe the permeability of the permeable hole under the influence of plugging; in addition, the calculation formulae for the accelerated consolidation effect of permeable piles and the variation of continuous drainage boundary interface parameters with permeable area ratio are given, which can provide references for engineering design.