目的 为探究盾构在下立交下穿越这一特殊工况所引起的周围环境变化规律.方法 采用三维有限元方法对盾构在下立交下长距离推进过程引起的地表及下立交变形进行了数值模拟,分析了盾构穿越下立交过程中导致的沿盾构方向和垂直于盾构方向的地表及下立交底板的沉降.结果 模拟结果与监测结果基本吻合,数值模拟的最大沉降量与监测值最大差值在lmm左右,误差不到10％.结论 两线通过后引起的底板沉降大于地表沉降,但未超出控制范围,结果显示扰动范围与盾构埋深有显著的关系.研究成果可以为同类工程问题提供参考借鉴.%In order to research the influence of shield tunnel crossing the underpass,3D - FEM is put forward to simulate shield tunneling long distance under underpass. According to the simulation results, settlement of ground surface and bottom slab of underpass along and perpendicular to the shield tunnel are analyzed in detail ; the discipline of ground surface and bottom slab of underpass settlement in different driving stages is uncovered, the settlement of slab is bigger than that of the ground surface;but not exceed the control range;the disturbance range of ground and slab are studied. The results showed that the disturbance range and depth of the shield have significant relationship;the settlements caused by shield tunneling in all kinds of conditions, such as different distance of two shields along the tunnel,different reinforcement methods,underpass existing or not,are analyzed. The results fit well with monitoring data;the difference(lmm)is limited to 10%. And the research can be used as a reference for similar projects.
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