Study On The Law Of Ground Deformation Caused By Shield Construction Based On Mindlin Solution

It is half a century since the first subway tunnel in China has been bulit.There are more than 40 cities which have been built,are to build or are building subway in China.The shield method is widely used in urban subway construction because of its high efficiency,high security and strong adaptability.However,this method affects the surrounding soil inevitably and causes surface subsidence or uplift.Excessive surface subsidence or uplift seriously affects safety of subway tunnel construction and normal use of road,viaduct,residential buildings and other structures on the subway crossing path,thus it is necessary to predict surface deformation caused by shield tunnel construction.In order to predict the impact of shield tunneling on sandy gravel strata more accurately,the method of predicting surface deformation caused by shield tunneling in metro tunnel is reviewed,and advantages and disadvantages of various methods are analyzed and summarized.Studying the stratum deformation caused by synchronous grouting during shield construction and assuming that soil is not drained,on the basis of the study of slurry diffusion radius and synchronous grouting pressure distribution in shield tunneling in sandy gravel strata,the calculation formula of 3D deformation caused by simultaneous grouting in shield tunneling of subway tunnel is deduced by Mindlin solution.On the basis of 3D deformation calculation formula caused by simultaneous grouting,considering soil loss and the friction of shell and shield,Sagaseta method is used to derive prediction formula of surface deformation of sandy gravel strata caused by shield tunneling.Taking the shield-driven tunnel works of Shengyang Metro for example to verify the correctness of the modified Sagaseta method,the modified Sagaseta method is used to predict surface longitudinal and horizontal settlement of sandy gravel strata induced by shield tunneling.Considering the distribution of simultaneous grouting pressure in sandy gravel strata,the process of shield construction is simulated by using MIDAS/GTS.The theoretical results of longitudinal and horizontal subsidence are compared with engineering monitoring results,Sagaseta theoretical results and numerical simulation results.The results show that the theoretical results are in good agreement with the engineering monitoring results,the method is more suitable for sandy gravel strata than the Sagaseta method,and the method can simulate the law of surface deformation better than the numerical simulation method.The modified Sagaseta method is of great reference to prediction of surface deformation of sandy gravel strata derived by shield tunneling...