基于管土接触特性的顶进力计算模型分析

Numerical model for jacking force based on pipe-soil contact characteristics

顶进力是顶管工程中管道结构设计、顶管机选型和工作井结构设计的决定性参数之一。为了更加准确地计算顶进力,假设泥浆压力作用下孔壁保持稳定,管道与孔壁土体发生部分接触,采用协调表面Persson接触模型分析管土接触角度和接触压力分布规律,在此基础上考虑管浆摩阻力影响推导出相应的顶进力计算公式。结果表明:管土接触角度和接触压力分布受管道和地层力学参数影响,软土层中管土接触角度可近似取180°定值,接触压力合力约为管道自重的1.35倍;当管道与岩层力学性质接近时,管土接触趋于点接触状态,接触压力的合力为管道自重,且工程实测顶进力与公式预测值相一致,证明其具有适用性。

Jacking force is one of the crucial parameters to decide design of pipe structure, selection of pipe jacking meachines and design of shaft structure for jacking projects. In order to more accurately calculate the jacking force, it is assumed that the excavation tunnel is stable under mud pressure and partial contact occurs between pipe and soil of hole wall. The Persson contact model for coordinated surface is used to analyze contact angle of pipe-soil surface and distribution of contact pressure. On this basis, the formula for calculating the jacking force is deduced considering influence of friction resistance between pipe and mud concurrently. The results show that the contact angle of pipe-soil and the distribution of contact pressure are affected by the mechanical parameters of pipe and formation excavated. The contact angle approximatively tends to be constant value of 180°, and the resulting force of contact pressure is about 1.35 times the pipe weight for jacking in soft soil. When the mechanical properties of pipe and rock are close to each other, the pipe and rock tend to be point contact state. The resulting force of contact pressure is equal to the pipe weight. The jacking force measured during jacking process is consistent with that predicted by the proposed formula, and its applicability is proved.