深厚软土地层地铁盾构换刀区土层加固范围优化

Optimization of Soil Layer Reinforcement Range in Deep Soft Soil Stratum Shield Cutter Replacement Zone

地铁盾构隧道在城市深厚软土地层中施工时会发生刀盘磨损,须在掌子面前方的土层加固区内进行换刀操作。为研究盾构换刀对掌子面前方土体的影响,以及获得合理的土体加固范围,采用PLAXIS-3D有限元软件建立了深厚软土地区地铁盾构隧道掘进三维数值模型,研究了盾构换刀时周围土体的变形规律,在此基础上通过正交试验的方法进行对比分析,并最终确定最优加固土体范围。结果表明:盾构换刀时,盾构隧道周围土体易发生较大变形,其中纵向变形最小,竖向变形次之,横向变形最大;隧道最大竖向变形位于隧道上方,最大横向变形位于盾构掌子面处,约为22 mm;竖向沉降随时间不断累积,需要通过加固换刀区周围土体来减小土体变形;随着横向加固长度的增加,土体沉降量先减小后缓慢增加,土层横向最优加固长度为8 m;在确定横向最优加固长度后,随着纵向和竖向加固长度的增加,加固后土体的竖向位移缓慢增加,纵向位移随加固长度的增大而减小,当纵向加固长度增大至10 m时,地面土体的纵向位移仅为0.2 mm;盾构换刀区土层最优加固范围为10.7 m(纵向)×10.7 m(竖向)×8.0 m(横向)的长方体区域。

Cutter head wear occurs in metro shield tunnel construction in city deep soft soil stratum.The cutter replacement must be completed in the soil layer reinforcement zone in front of tunnel face.To study the influence of shield cutter replacement on soil mass in front of tunnel face and to obtain reasonable soil layer reinforcement range,3D numerical model of metro shield tunnel excavation in deep soft soil area is built using PLAXIS-3D finite element software,and the deformation law of surrounding soil during shield cutter replacement is studied.On this basis,the optimal soil layer reinforcement range is finally determined through comparative analysis by orthogonal test method.The results show that during shield cutter replacement,the shield tunnel surrounding soil is prone to large deformation,while the longitudinal one is the least,vertical one the second and transverse one the most;tunnel maximum vertical deformation is on tunnel top,the maximum transverse one is near shield tunnel face,about 22 mm;vertical deformation accumulates over time,the reduction of which requires reinforcement of cutter replacement zone surrounding soil mass;with the increasing transverse reinforcement length,the soil settlement decreases first then increases,and the soil layer transverse optimal reinforcement length is 8 m;after determining the transverse optimal reinforcement length,with the increase of longitudinal and vertical reinforcement length,the vertical displacement of reinforced soil gradually increases,and the longitudinal displacement decreases as the reinforcement length increases,when the longitudinal reinforcement length is increased to 10 m,the longitudinal displacement of ground surface soil is only 0.2 mm;the optioptimal reinforcement range shield cutter replacement zone soil layer is a 10.7 m(longitudinal)×10.7 m(vertical)×8.0 m(transverse)cuboid zone.