基于PFC-FLAC耦合的砂土中桩基轴向承载特性分析

Analysis of bearing mechanism of single pile in sand under vertical load based on PFC-FLAC coupling method

随着海上风电的蓬勃发展,单桩基础因其适用性和经济性较好而得到广泛应用,且单桩基础设计直径和长度在逐渐增大。桩长的增加使得桩-土相互作用模式区别于短桩,力的传递过程发生了明显的改变。为探究单桩基础轴向承载机制,以密实的福建标准砂为材料,基于室内三轴试验标定了土体参数,采用连续-非连续耦合方法,利用PFC-FLAC软件建立耦合模型模拟了桩基轴向静载过程,以宏微观相结合的角度研究桩土间相互作用机理,揭示密实砂土中荷载传递规律。结果表明:桩身轴力随荷载增加逐渐向下发挥,加载初期桩端处不承担承载力;加载过程中,桩土间相互作用使桩身周围土体逐渐致密,且主要承担荷载区域深度为15 D~30D,孔隙比变化更大,应力集中更为显著,表现为明显的摩擦桩特性。

The rapid development of offshore wind power industry has led to thewidespreaduseof single pile foundations due to their applicability and cost-effectiveness.Asthe design diameter and length of pile increase,the behavior of the pile-soil interaction model different from that of short pile,resulting in notable changes in the force transfer process.This paper aims to investigate the load-bearing mechanism of single pile under vertical load,soil parameters were calibrated based on indoor triaxial tests with dense Fujian standard sand as the material.Furthermore,a model was established using the continuous-discontinuous coupling method and PFC-FLAC software to simulate the vertical static loading process of pile foundation,and the interaction mechanism between pile and soil was studied from the perspective of macro and micro combination.The findings reveal that the axial force along the pile gradually engages with the increase of load and the pile tip scarcely bears any load at the initial loading stage.Throughout the loading process,the surrounding soilundergoes gradual densification because of the interaction with the pile.Significant changes in porosity and stress concentration,particularly in the regions 15 D~30D where the load is primarily borne,indicate distinctive characteristics of friction piles.