砂土中桩与桩相互作用数值模拟研究

Numerical simulation of pile-pile interaction in sandy soil

为了研究双桩系统沉桩过程中后沉桩对先沉桩的影响,采用PFC2D程序,对双桩系统沉桩过程进行颗粒流数值模拟,旨在得出桩的土塞高度、沉桩阻力及先沉桩0.2 m埋深处侧向压力的变化规律。模拟结果表明:沉桩过程中,管桩直径越大,形成的土塞相对高度越大,沉桩产生闭塞效应的可能性越小;先沉桩贯入过程中,桩周上部土体产生竖向位移,密实度下降,而下部土体压缩变形,密实度增加,进而使得后沉桩土塞增量填充率前期大于先沉桩,而后期小于先沉桩;桩端阻力在沉桩过程中前期增加较快,后期趋于稳定,存在临界深度为5.3D左右;沉桩阻力受到沉桩顺序影响,后沉桩的沉桩阻力明显大于先沉桩;在后沉桩贯入0.2 m时,先沉桩0.2 m埋深处侧向压力达到峰值点,但随桩体继续贯入,先沉桩侧向压力显著下降,且随开口管桩直径增大而减小。

In order to study the effect of post-pile on pre-pile during the pile-sinking process of dual-pile system,PFC2D program was used to conduct particle numerical simulation of the pile-sinking process of the dual-pile system,aiming at obtaining the change law of the soil plug height of the pile,the pile resistance and the lateral pressure change at the depth of 0.2 m.The simulation results show that the larger the diameter of the pipe pile during the pile sinking process,the greater the relative height of the soil plug formed,and the less likely the piled pile has the occlusion effect.In the process of pre-pile sinking,the soil around the pile will produce vertical displacement and the compactness of the soil will decrease,while the lower soil compresses and deforms,and the compactness increases.As a result,the incremental filling ratio of the post-sinking pile is greater than that of the pre-sinking pile in the early stage,and it is less than that of the post-sinking pile in the later stage.The pile end resistance increases rapidly in the early stage of the pile sinking process.It tends to be stable,and the critical depth is about 5.3D.The pile resistance is affected by the order of pile driving,and the pile-sinking resistance of the post-sinking pile is significantly larger than that of the pre-sinking pile.When the post-pile is penetrated into 0.2 m,the lateral pressure in the buried depth of 0.2 m of the pre-pile reaches the peak point,but as the pile continues to be penetrated,the lateral pressure of the pre-pile is significantly reduced,and decreases with the increase of the diameter of the open pipe pile.