深埋小净距多线平行盾构掘进相互作用分析

An analysis of interaction of deep buried close approaching multi-line parallel shield tunneling

浅覆软弱地层中小净距盾构隧道施工时,后行隧道施工显著影响先行隧道安全,但深埋情况下,由于地下岩土层的复杂性和不确定性,使得多线隧道施工时先行隧道的变形变得复杂。以上海硬X射线土建部分盾构隧道为背景,结合有限元数值模拟,分析了深埋小净距盾构隧道施工时的相互影响,并对不同的盾构参数进行了敏感性分析。研究表明:随着后行隧道的开挖,先行隧道管片的变形增量变化基本呈双峰特征。当采用左-右-中方式开挖时,管片变形增量呈一大一小双峰分布;而采用中-右-左方式时,管片竖向变形增量峰值的大小和方向相同,而水平变形增量的峰值相同,方向不同;随着浆液弹性模量的增加,管片竖向变形增量变化较大,水平变形增量基本不变;随着顶推力的增大,管片的变形也在相应地增大,并在支护应力比为0.6~0.7之间时达到稳定;地下水的存在对管片竖向变形有着一定的影响;通过对比2种开挖方式管片的变形收敛情况,选择左-右-中次序开挖比较安全。

Construction of a second shield tunnel in shallow soft strata may reduce the safety of the first shield tunnel,especially when the clear spacing is very small.However,in the case of deep burial,the deformation of the first tunnel becomes complicated due to the complexity and uncertainty of the underground soil layer.With the shield tunnel of hard X-ray civil construction in Shanghai as the background,combined with finite element numerical simulation,the mutual influence during the construction of the deep-buried shield tunnels with small clear spacing is analyzed,and the sensitivity analysis of different shield parameters is carried out.The research results show that with the excavation of the later tunnel,the deformation increment of the first tunnel segment is basically bimodal.When the left-right-middle method is used,the deformation increment of the segment is of a big and a small bimodal distribution.In the middle-right-left method,the peak value of the vertical deformation increment is the same in size and direction,while the horizontal is the same in different directions.With the increase in the elastic modulus of grouting,the vertical deformation increment of the segment changes greatly,while the horizontal deformation increment is basically unchanged.When the pushing force increases,the deformation of the segment increases,and it reaches a stability when the supporting stress ratio is between 0.6-0.7.The existence of groundwater has a certain effect on the vertical deformation of the segment.By comparing the deformation convergence of the two excavation methods,the left-right-middle sequence of excavation is finally selected.