沉桩过程中钙质砂颗粒破碎特性模拟研究

基于二维离散单元法，对沉桩过程中钙质砂颗粒破碎情况进行了模拟。采用簇粒来模拟易破碎的钙质砂颗粒，并用形状与变形特性相同的聚粒单元来模拟不可破碎颗粒，对这两种单元特性进行对比，分析不同桩型的沉桩过程、桩周土体的力学响应、沉桩过程中钙质砂的颗粒破碎现象。结果表明：破碎颗粒将引起桩侧土体级配的重新调整，与桩体接触好于不可破碎土体；桩处于颗粒破碎的钙质砂中，其沉桩速度较快，对地基土扰动小于未发生颗粒破碎的情况；对于不同桩型、不同土层，桩体压入过程中，桩周土体应力场分布具有相似性；靠近桩端附近，土中水平应力和竖向应力急剧增大，形成应力核；同等条件下发生颗粒破碎的钙质砂地基土中，桩端应力峰值高于不可破碎土体。

Discrete element simulation of crushing behavior of calcareous sands during pile jacking

Based on two-dimensional discrete element method, this paper simulates the calcareous sand particle of easily-crushed feature as a cluster cell. It uses the clump cells with the same shape and deformation characteristics to simulate the particles without crushing. The jacking processes for different types of pipe piles are simulated with the model to analyze the meso-mechanical behaviors and breakages of the calcareous sands. The results show that the particle breakage can cause the gradation readjustment, resulting in a better contact between the particle and the pile. The driving speed in calcareous sands is relatively fast. There is a smaller disturbance to the foundation soil. The stress field around the pile has the same tendency. The stresses near the pile tip increase dramatically and result in the formation of the stress nucleus. Under the same surrounding conditions, the horizontal and vertical stresses of crushable calcareous sands are obviously greater than those of the unbroken soil.