地铁盾构施工地层变形预测及数值分析

Numerical analysis of stratum deformation induced by tunnel boring machine construction for metro

以某城市地铁在建盾构隧道为研究对象,借助数值仿真建立了三维盾构施工有限差分计算模型,给出了盾构施工引起的地层变形三维地层损失预测方法,并对盾构施工地层竖向变形及水平变形计算结果进行对比分析.结果表明,隧道横向地层变形接近"V"形分布,形成的地表沉降槽宽度约为6倍隧道直径;盾构前方土体产生隆起,开挖面后方表现为沉降,沿盾构掘进方向近似呈倒"S"形,并在开挖面前后3倍直径以外逐渐趋于稳定;地层水平变形左右两侧反对称,距隧道中心约1倍直径处地层水平变形值最大,6倍直径以外地层水平变形基本不受施工影响;随着埋深的增加,地层水平变形值减小,隧道拱腰上下一定范围土体向洞外移动.所得结论对城市地铁盾构隧道设计与施工变形控制有指导意义.

On the basis of the case study of the subway tunnel by tunnel boring machine construction and adopting the finite difference software FLAC, we establish three-dimensional stratum-structure model to simulate the dynamic process of tunnel boring machine construction. We put forward an improved three-dimensional prediction method of stratum deformation caused by tunnel boring machine construction based on stratum loss theory. The horizontal and vertical deformations of stratum are analyzed and compared with theoretical results. The results indicate that transver- sal stratum vertical deformation induced by tunnel boring machine construction presents a V-shaped curve. The width of settlement tank is about six times the tunnel diameter. Longitudinal stratum vertical deformation induced by tunnel boring machine construction demonstrates a S-shaped curve. The front excavation surface is uplifted and the back excavation surface is settled. It is changed gradually stable when the distance is greater than three times the diameter from the excavation surface. The curves of stratum horizontal deformation are the anti-symmetrical distribution, the maximum horizontal deformation is happened at about one time the diameter from the tunnel center. About six times the diameter from the tunnel center will be not influenced by shield construction. With the buried depth of tunnel getting bigger, the deformation of stratum horizontal gets smaller and the soils of tunnel arch haunch move to outside of the hole. The conclusion can be used and referenced for the design and construction of subway tunnel.