盾构下穿对既有铁路路基影响的模型试验研究

为研究盾构隧道开挖对既有铁路路基的影响，基于相似比理论建立室内大型试验模型，模拟盾构开挖扰动作用下周围土层及既有铁路路基的受力变形过程。结果表明:模型试验能较好地反映盾构下穿对土层及地表线路的影响；盾构隧道轴线方向各土层土压力变化较两侧明显，其中在一倍洞径范围内土体是受扰动影响的重点区域；模型试验中盾构下穿开挖导致既有线路沉降变形呈近似线性，若增加埋深，既有路基沉降速度及沉降量将大幅降低。建议在盾构施工前对既有铁路的下穿段路基进行加固，确保行车安全。

Model Test Study on Influence of Shield Tunneling Underpass on Existing Railway Subgrade

In order to study the influence of shield tunnel excavation on the existing railway subgrade, an indoor large-scale experimental model is established based on the similarity ratio theory and the deformation process of surrounding soil layer and existing railway subgrade under the influence of shield construction is simulated. The results show that model test can better reflect the influence of shield tunneling underpass on soil layer and surface line. The earth pressure changes of the soil layers in the axial direction of the shield tunnel are more obvious than the two sides and the soil in the double holes diameter is the key area affected by the disturbance. In the model test, the settlement deformation of the surface line caused by the shield tunneling is approximately linear. If the buried depth is increased, the settlement speed and settlement volume of the existing subgrade will be greatly reduced. It is suggested to reinforce the subgrade of the underpass section of the existing railway before shield construction to ensure the safety of traffic.