Numerical Simulation-Based Analysis of the Effects of Different Soil Conditions on Shallow-Buried Shield Tunnels

为研究不同土性条件下，上下台阶法施工对浅埋盾构隧道稳定性的影响规律，文章利用数值模拟手段，以砂土与黏土两种典型土层为研究对象，建立了隧道施工过程的数值分析模型。对比分析了砂土与黏土浅覆土层条件下，上下台阶法隧道开挖过程中隧道围岩变形、地表沉降及隧道拱顶与拱底变形的差异。结果表明土层性质显著影响施工过程中围岩与结构的响应特征，砂土条件下围岩变形与地表沉降更为敏感，施工扰动影响范围相对较大；而黏土条件下围岩稳定性相对较好，施工扰动影响范围相对较小。本文研究成果可为浅埋隧道施工方法选择、施工风险评估及优化设计提供重要参考依据。To investigate the influence of different soil properties on the stability of shallow-buried shield tunnels constructed by the bench excavation method, numerical simulation models were established for two typical soil conditions—sand and clay. Comparative analyses were conducted on the deformation characteristics of surrounding rock, ground surface settlement, tunnel crown, and invert deformation during bench excavation under shallow cover conditions. The results demonstrate that soil properties significantly affect the response characteristics of surrounding rock and tunnel structures during construction. In sandy soils, deformation of surrounding rock and surface settlement are more sensitive, resulting in a relatively larger range of construction disturbance. In contrast, clay soils exhibit better stability of the surrounding rock and a comparatively smaller area of construction disturbance. The findings provide important references for construction method selection, risk assessment, and optimal design of shallow-buried tunnels.