Study On Laws And Control Measures Of Ground Settlements Caused By Shield Tunneling

The shield machine in the course of shield tunneling will generally rise to ground settlement on the top of the tunnel,and there will be a tunnel settlement in tunnel construction and operation, a direct impact on the surrounding buildings and underground facilities in the normal use. It is a very important issue of practical engineering significance that how to reduce the construction disturbance to soil level,analysis of ground settlement, and investigate the laws of ground settlement in the tunnel construction.On the base of a large number of relevant papers and literature, the paper studied more in-depth on the ground settlement caused by shield tunneling. Firstly, the paper summarized the theory of our predecessors, analysis of ground settlement resulting mechanism, the factors and the general law of ground settlement. Secondly, in the background of the shield tunneling from Gaozeng Station to New Airport Station in Guangzhou Metro,the paper analysied the shield tunnel boring and the ground settlement by tunneling with finite element software MIDAS/GTS,then compared with numerical simulation results and monitoring data. Thirdly, still with finite element software MIDAS/GTS,this paper focused on studying on how the factors including upper casing, tail shield grouting, tunneling pressure and two-lane tunnel's construction program affect ground settlement. Finally, this paper put forward reasonable practical measures on how to control ground settlement.There are some conclusions from the study in this paper:(1)Results from finite element software MIDAS/GTS and project monitoring data are basically consistent, it verified the reliability of numerical simulation results by MIDAS/GTS.(2) Thicker top casing makes litter ground settlement with the formation depth increases, the horizontal strata maximum settlement amount is even greater.(3)When simulating the tail shield grouting with equivalent circle zone, it found that the material parameters of equivalent circle zone affect little on ground settlement, while the material thickness of equivalent circle zone affect on ground settlement obviously.(4) The Driving pressure impacted on the vertical ground settlement greatly, it should be controlled when constructing.(5) In double line tunnel constructing, there is little difference about ground settlement wheter the two line constructed at the same time and the same direction or one first then another.while and the excavation and the completion of a tunnel then turn around the other one. But, when using the latter methods, because of the subsidence superimposition, the ground settlement of the two centers of two lines is not equal, the settlement tanks are unsymmetrical.