地铁盾构下穿立交危险断面的数值模拟

依托合肥地铁盾构下穿五里墩立交工程项目，结合有限差分软件计算，分析施工过程中4个危险断面的地表变形及桩基变形规律. 研究表明:右线隧洞盾构引起地表沉降槽呈单峰型，左线隧洞盾构后沉降槽呈双峰型；当左右线隧洞距离较近时沉降量变化仍呈现单峰型，当左右线隧洞距离较远时，地表沉降量变化则呈现双峰型；桩基距离隧洞越近，其沉降变形越大，实际情况也会越危险；地铁近距左右线隧道盾构依次开挖对土体产生的扰动具有叠加效应，且叠加效应明显. 以数值分析来考虑区间变形，方法简洁可行，从思路上为类似工程分析提供参考.

Numerical Simulation of Dangerous Sections of Shield Tunnel Under-Passing Flyover Bridges

The deformation of ground and pile foundation of four critical fracture surface in constructing Hefei subway shield under passing the Wulidun flyover bridges was analyzed by the finite difference calculation software. The result shows that the tunnel shield on the right-side brings the ground subside to be unimodal，and the left-side one causes the ground subside to be bimodal；the variation of ground deformation is still of unimodal pattern when the distance between two tunnels is relative short，and the variation of ground deformation becomes bimodal when the distance is longer；the actual situation is more dangerous when the variation of ground deformation is larger and the distance between pile foundation and tunnel is shorter. The construction of short-gap tunnels in turn has a broadly apparent superimposed effect on soil mass. The method is concise and practicable，providing a reference for similar projects’ analysis.