软硬地层下双顶管掘进参数对管片及地层的影响性研究

软硬地层中双顶管掘进参数不当所导致的周围土体变形、姿态偏离、刀盘磨损等问题在实际工程中屡有发生。以南宁平花河顶管为工程背景，通过数值模拟研究软硬地层中不同掘进参数组合对周围地表沉降及管片应力的影响。得到结论如下：开挖面掘进压力对地表变形的影响呈现出非线性特征，地表沉降及其减小的速率随着掘进压力增大而减小；注浆压力与横向地表沉降之间呈现出线性递减的趋势，影响区域约为双隧道中心2倍隧道直径范围内；管片最大Mise应力与盾尾注浆压力、千斤顶推力均呈现线性递增的关系，当注浆压力、管片千斤顶推力分别增加10 kPa，每环管片的最大Mises应力相应分别增加64 kPa、17 kPa；开挖面掘进压力增大时，管片应力呈向着非线性递增的趋势，管片应力变化也相应减小，掘进压力从0kPa变化至20 kPa时的管片应力变化率为40~60 kPa的1/4~1/3

Influence of the Driving Parameters of the Double Pipe Jacking in Soft-hard Strata on Segments Strata

In the upper-soft and lower-hard stratum, it is frequent problem that improper driving parameters of double pipe jacking causes deformation of surrounding soil, deviating attitude of pipe jacking, cutter head damage. Based on the engineering background of Pinghua River pipe jacking in Nanning, the influence of different combination of tunneling parameters on the surrounding surface settlement and segment stress in soft and hard strata was studied by numerical simulation. It is concluded that the influence of the driving pressure on the surface deformation is non-linear, and the surface settlement and its decreasing rate decrease with the increase of the driving pressure; there is a linear decreasing trend between grouting pressure and lateral surface settlement. The influence area of grouting pressure is about 2 times of the diameter of the tunnel from the center of the double tunnel. The maximum stress linearly increases with grouting press and the thrust of jack. When the grouting pressure and the thrust of jack were increased by 10 kPa, respectively the maximum Mises stress of each segment was increased by 64 kPa and 17 kPa; the segment stress nonlinearly increases with the increasing tunneling press in the excavation face and the change of the segment stress decreases correspondingly. When the tunneling pressure is changed from 0 kPa to 20 kPa, the change rate of segment stress is 1/4 to 1/3 of that from 40 to 60 kPa.