大型地下方厅多导洞施工力学效应分析

针对北京城铁 13号线东直门站地下方厅开挖跨度大、覆盖层薄、地质条件极差的施工难题 ,笔者采用三维有限元数值模型 ,模拟开挖支护施工流程 ,考虑到围岩介质的复杂特性 ,施工作业方式 ,包括分布开挖工序 ,支护结构形式和施作时机 ,以及开挖面推进过程中的空间效应 ;按形变压力理论 ,选用“连续体”计算模型 ,采用增量变弹性法和增量叠代的混合法进行计算分析 ,对多导洞开挖支护施工方案进行了计算分析 ;基本掌握了在覆土厚度小的情况下开挖大跨平顶直墙方厅时 ,周围土体的应力分布特征和变形特性 ,对于优化施工方案、修改支护参数、采取局部加固措施起到了重要作用。实践表明采用多导洞施工方案是科学合理的 ,有利地保证了周边环境和施工安全。

Mechanical Effect Analysis of Large-scale Underground Square Mall by the Multi-pilot-cavity Construction Method

Due to the difficulties of large span, shallow-embedded, and poor geological condition in Dongzhimen Station of Beijing Urban Railway Line 13, spatial FEM numerical model is adopted to simulate the process of excavation and support. Considering complicated rock characters and construction method which includes excavation, support type, support time and the spatial effect during excavation, the multi pilot cavity construction scheme is calculated and analyzed by continuous calculation model and combined methods of incremental changeable elastic with incremental repeat. The stress and strain distribution characters of surrounding rock are very helpful to optimize construction scheme, modify support parameters and take some local stabilization measures while constructing large span, straight wall square hall. The practice indicates that multi pilot cavity construction method is very reasonable and reliable to guarantee construction safety and surrounding environment.