洞桩法地铁车站导洞开挖方式对地表沉降的影响分析
Analysis of Influence of Guide Tunnel Excavation Method on Surface Settlement in Subway Station Constructed by PBA Method

目的：本文依托西安地铁8号线小白杨站实体工程，为探究洞桩法地铁车站导洞施工阶段，导洞断面施工方法和开挖错距对地表沉降及支护结构变形的影响。方法：采用数值模拟与现场监测的方式。结果及结论：研究结果表明：对于单层三导洞洞桩法车站而言，导洞开挖方法采用预留核心土弧形开挖法以及“先中后边”错距20 m施工顺序，更有利于控制地层及支护结构变形；在导洞断面施工方面，全断面开挖引起的地表沉降最大值均大于相应施工顺序下预留核心土弧形开挖，沉降差异介于8 mm以内；在开挖错距方面，相邻导洞掌子面距离越大，施工引起的地表沉降越小，最大地表沉降以相邻错距10 m为基准，15、20、25、30 m时，依次减小了6%、5.3%、2.5%、1.9%，且当错距大于20 m时，地表沉降的减小趋势已不明显。相关研究成果可为今后类似工程施工提供借鉴意义和参考价值。
Objective: Based on Xiaobaiyang Station of Xi’an Metro Line 8, this paper studied the influence of the construction method of the pilot tunnel section and the excavation stagger distance on the surface settlement and the deformation of the supporting structure. Method: This paper adopts numerical simulation and field monitoring. Result & Conclusion: The results show that: for the single-layer three-pilot tunnel station constructed by PBA method, The excavation method of the guide tunnel adopts the arc excavation method of reserving the core soil and the construction sequence of “first, middle and back” is 20m apart, which is more conducive to controlling the deformation of the stratum and the supporting structure; in the construction of pilot tunnel section, the maximum ground settlement caused by full-face excavation is greater than that caused by arc excavation of reserved core soil under the corresponding construction sequence, and the settlement difference is within 8 mm. In terms of excavation offset, the larger the distance between the adjacent heading face, the smaller the surface settlement caused by construction. The maximum surface settlement is based on an adjacent displacement of 10 m, and decreases by 6%, 5.3%, 2.5% and 1.9% respectively at 15, 20, 25, and 30 m. When the offset is greater than 20 m, the decreasing trend of surface settlement is not obvious. The relevant research results can provide reference for similar engineering construction in the future.