成都地铁卵石层中盾构施工开挖面稳定性研究

随着我国社会经济的发展，越来越多的城市开始规划和修建地铁，在此期间，部分城市在地铁建设中遇到了地质条件非常复杂的砂卵石土层，特别是正在建设中的成都地铁1、2号线，区间隧道几乎全部从卵石土层中穿越，根据设计，成都地铁1、2号线部分区间隧道采用加泥式土压平衡盾构法施工。利用土压平衡式盾构施工时，开挖面支护土压力控制是保证掘进顺利进行的关键，目前国内外在这方面的研究主要集中于砂土和黏性土，关于卵石土盾构隧道开挖面变形与破坏的研究很少。基于此，根据卵石土具有强烈离散特性的特点，利用颗粒离散元数值方法，对卵石土层土压平衡式盾构施工中开挖面支护应力不足引起开挖面的变形及破坏问题进行了分析研究，探讨了隧道开挖面变形及破坏问题。研究结果显示:（1）开挖面极限支护应力远小于土体原位静止土压力；（2）开挖面失稳后，开挖面前部的滑动块为一曲面体。这为卵石土地层中盾构开挖面控制压力的确定提供参考。

Study of face stability of cobble-soil shield tunnelling at Chengdu metro

In recent years, with China's social and economic development, more and more cities began to plan and build metros. Meanwhile, the metro construction encountered the sandy pebble soil in some cities, especially the running tunnels of Chengdu Metro line 1 and 2 are almost both need to cross the sandy cobble soil. According to the design, Chengdu metro No.1 and No.2 lines will be constructed by mudding-type earth pressure balance shield. And during shield tunnelling, the face stability control that will be a key operation to ensure the construction can be carried through smoothly. Nowadays, the study of supporting earth pressure is mainly focused on sandy and clay soil; but the study involving the face movement and collapse of cobble-soil is seldom. So based on the heavily discrete characteristics of cobble-soil, the paper analyzes the shield tunnel face deformation and failure while the support pressure is lower than the limit pressure which constructed by using earth pressure balance method and the deformation and failure of excavated face by discrete element method. The results show that: (1) supporting earth pressure of tunnel face is lower than earth pressure at rest; (2) after the face loses stability, the slider ahead of the tunnel face is a surface body. The results will give reference to determine the face control pressure of shield tunnelling.