Study On Ground Surface Settlement Caused By Construction Of Urban Shallow Subway Tunneling In Weak Surrounding Rock And Its Control

The ground surface settlement caused by large-span subway tunnel in urbanshallow buried weak surrounding rock is always an particular topic for the subwaytunnel builders, and it is also a key issue that is very difficult to control and urgent to besolved. Ground deformation will be inevitably aroused by underground subway tunnelwithin the rock mass. When the ground deformation reaches a certain degree, theground structures and the peripheral ecological environment will be damaged seriously,and even people’s life and property will be endangered. Therefore, studying the problemof ground settlement caused by tunneling, exploring the rule of settlement variationcaused by different excavation methods, and proposing effective settlement controlmeasures on the subway tunnel design, construction and operational safety are of greatsignificance. The ground surface settlement during the subway tunnel construction inShi Xie district of Chong Qing subway line one was simulated and analyzed in thispaper.Firstly, the main theory of tunneling-induced ground movement is introduced, andthe law of stratum deformation aroused by the construction of large-span subway tunnelin Urban Shallow buried weak surrounding rock is summarized. Meanwhile, the law oftransverse and longitudinal deformation is elaborated in detail in this paper.Secondly, the control theory and strategies of the larger ground settlement causedby tunneling and the details of ground settlement are introduced. In addition, the controlstandard and permissible values of sedimentation are described. According to thespecific measures and effects of the sedimentation control, the conclusions withadopting reasonable control measures can effectively control the ground surfacesettlement are concluded.Again, the application of ANSYS software in underground engineering，DP yieldcriterion and the basic analysis procedure of finite element method are introduced bythis article. Hydro geological conditions outlined relying on the project introduced isprepared for selecting a reasonable material parameter. With different constructionmethods and the strata pre-reinforcement method are adopted by works on the basis ofthe numerical simulation. The best construction method—double-side-drift method isconcluded by analyzing and comparing of settlement changes for each case. The results show that the strata pre-reinforcement method can reduce ground surface settlementwell after reinforcement measures taken against the best construction method.Finally, strata deformation situation caused by the tunnel construction is analyzedbased on engineering monitoring data. Sedimentation analysis results consistent withthe numerical simulation results are further validate the reliability of the numericalsimulation results. Meanwhile, the rationality of double-side-drift method and the stratapre-reinforcement method in Chongqing metro line1stone tunnel can effectivelycontrol the ground surface settlement are demonstrated.