浅覆土超大直径泥水盾构隧道开挖面稳定性研究

Study on Face Instability of Shallow Slurry Shield Tunnel with Large Diameter

为研究盾构隧道采用不同支护介质时开挖面稳定性与支护力的关系,探索开挖面失稳破坏发展规律,采用ANSYS对盾构隧道三维数值模型进行了优化,并用FLAC3D分别对泥浆支护和气体支护两种工况不同支护力下开挖面的稳定性进行了数值模拟,分析了开挖面土体的应力、应变、位移速度等模拟结果。主要结论如下:随支护力减小开挖面首先产生局部破坏,采用泥浆支护时局部破坏出现在开挖面中部,而采用气体支护时则在底部区域,两种工况下开挖面整体破坏均与三维楔形体破坏模型近似;开挖面土体应力(SXX,SYY和SZZ)与支护力大小存在正相关性,其中SYY分布规律与支护力保持一致;随支护力的减小,开挖面水平最大位移与地表最大沉降量增大速度均先慢后快,地表最大沉降点在开挖面前方0.5倍洞径处,且横向沉降槽宽度大于纵向沉降槽;土体位移速度和剪切应变增量与开挖面稳定性存在较强关联性,二者在开挖面产生整体破坏时均呈现规律性变化。

In order to study the relationship between the stability of the excavation face and the support pressure and the law of its failure development of the shield tunnel,The three-dimensional numerical model of the shield tunnel is optimized by ANSYS,and the influence of the support pressure on the stability of the excavation face under the conditions of mud support and gas support was simulated by FLAC3D.And then,the simulation results of stress,strain and displacement velocity of the excavation face under different support ratios are analyzed.The main conclusions are as follows:As the support pressure decreases,the excavation face first collapse locally,and local collapse occurs in the middle area of excavation face with mud support,while occurs in the bottom area with the gas support is used.There is a positive correlation between the stress(SXX,SYY and SZZ)of the excavation face and the support pressure,and the distribution of SYY is consistent with the distribution of support pressure.The maximum horizontal displacement of the excavation face and the maximum settlement of the ground surface are both increase slowly first and then quickly with the decrease of support pressure,the maximum surface settlement point in front of the excavation face 0.5D position,and the lateral settlement trough width is larger than the longitudinal settlement trough.There is a strong correlation between the displacement velocity and the shear strain increment and the stability of the excavation face,both of them show regular changes when the whole excavation surface collapses.