被动桩侧向土压力的三维数值模拟

Three-dimensional numerical analyses of lateral soil pressure on passive pile

运用岩土数值计算程序FLAC^(3D)对土体沿深度发生均匀侧移、桩基两端可简化为铰接情况下的被动单桩的侧向土压力进行了研究,其中土体采用摩尔-库伦本构关系,桩基采用线弹性本构关系,桩土之间建立接触面。研究表明:桩侧土压力随着土体侧向位移增大而增大,当达到极限状态时在浅层土体内桩侧极限土压力随深度增加而增大,达到一定深度后,桩侧极限土压力随深度增加基本保持不变;桩周粗糙度是影响桩侧极限土压力大小的重要因素;桩土相对刚度对桩基位移、剪力、弯矩和桩侧极限土压力分布有较大影响。另外,分析了桩侧土压力-桩土相对位移关系曲线(p-δ曲线)的形状以及达到极限土压力所需的桩土相对位移,并将计算结果与前人研究结果比较,得出两者具有较好的一致性且本文结果有所改进。

The lateral ultimate soil pressure of the passive pile has not been completely solved,and many researchers have done studies of this problem. Using the explicit finite difference code FLAC^（3D）（Fast Lagrangian Analyses of Continua）,the lateral ultimate soil pressure of a single passive pile with pined-head and pined-tip condition and uniform soil movement was investigated,the Mohr-Columb elastic-plastic constitutive model was applied to a model for the non-linear stress-strain soil behaviour,the pile was assumed to have linear elastic behaviour,the interface model incorporated in FLAC（3D）code was used to simulate the soil / pile contact. The results given by the numerical analysis indicated that the soil pressure acting along the pile shaft increased with the soil movement increasing. While reaching the limit state,in the shallow soil the lateral soil pressure increased with increase of embedded depth,but in the deep soil the lateral soil pressure almost remained constant with increase of embedded depth. The roughness of the pile had an important influence on the lateral soil pressure. The relative stiffness between pile and soil had important influence on the displacement,shearing force,moment and lateral soil pressure of the pile. The shape of the soil pressure versus the relative soil-pile displacement curves and the magnitude of relative displacement to mobilize the ultimate soil pressure were analyzed. The research results are in good agreement with those reported by other researchers and better than the latter.