Underlying Shield Tunnel Deformation Effected By Pit Excavation

With the rapid development of urban construction, foundation construction will inevitably appear at the top of the subway tunnel. Excavation is bound to affect the stress and deformation of the subway tunnel below it. Currently the research on underlying shield tunnel deformation effected by pit excavation is still not perfect, this paper used finite element software, and analyzed tunnel deformation factors, to study underlying shield tunnel deformation effected by pit excavation. this paper endeavored to do the following work: Firstly, this paper described the background, summarized the research situation about underlying shield tunnel deformation effected by pit excavation at present, and it proposed the research questions to be addressed in this thesis.Secondly, it analyzed the deformation factors of subway tunnel, introduced two methods to calculate tunnel heave caused by excavation, this two methods are"Residual stress theory method"and"Classical theory of law Mindlin". Next, it introduced the method to calculate equivalent stiffnesses of shield tunnel.Thirdly, based on the above, using the South Korean rock tunnel structure special software MIDAS/GTS with finite element analysis function and numerical simulation method, to study underlying shield tunnel deformation effected by pit excavation, from the whole excavating process, the effect of excavation, the equivalent stiffnesses coefficient of shield tunnel, the elastic modulus values of soil near the tunnel, and so on, last it analyzs by according to projects - Guangzhou Dongfeng Plaza Phase V Project. The results show that: Vertical displacement is the main displacement of the tunnel; the space effect of excavation significantly affects the tunnel deformation; the smaller the equivalent stiffness values of shield tunnel is, the greater the tunnel deformation is; the smaller the elastic modulus values of soil near the tunnel is, the greater the tunnel deformation is, and the tunnel deformation is as a linear increase with reciprocal of the elastic modulus values of soil near the tunnel.