Study Of Longitudinal Uneven Settlement In Shield Tunnels Under Differential Strata Due To Dynamic Load

With the rapid development of urban rail transport,the opening of the metro has greatly facilitated the travel of the public and brought great convenience to the life of residents.However,a series of problems caused by train vibrations during the operation of the metro have also aroused widespread concern.When the underground crosses the differential strata,the tunnel structure will inevitably produce uneven settlement,which will have a certain impact on the safety of the tunnel structure and the safety of the trains.In this context,the paper relies on the project of the Natural Science Foundation of Hebei Province(Name: Research on Long-term Uneven Settlement of Metro Shield Tunnel in Differential Ground;No.E2015210105),which adopts a combination of data research,indoor model tests,and numerical simulations,with the following main research contents.(1)For the influence of train vibration on shield tunnel lining pipe sheet,indoor model similarity tests were designed combined with model test similarity theory to determine the similarity ratios of shield lining pipe sheet,shield lining pipe sheet joint,soil body,and applied load in the test,similar materials of the above structures and their ratios were determined,and train vibration loads were simulated by using exciters.(2)Model similarity tests on the effect of train vibration on the shield tunnel lining sheet were carried out to investigate the effects of the tunnel burial depth,the underlying weak soil layer,the surface load and location,and the train travel speed on the mechanical properties of the shield tunnel lining and the earth pressure respectively.(3)Numerical methods are used to study the longitudinal uneven settlement and deformation characteristics of the shield tunnel lining under the vibration load of the train,and to analyze the distribution of soil pressure on the lining under the depth of the tunnel,the underlying weak soil layer,the surface load and location,and the train travel speed.By comparing the numerical and test results,the reasonableness of the above laws and the reliability of the parameters selected in the numerical analysis are analyzed.(4)Numerical methods are used to analyze the longitudinal uneven settlement and deformation characteristics of shield tunnel lining sheets under the action of moving train loads.The laws of soil pressure distribution of lining sheets under tunnel burial depth,underlying weak soil layer,surface load and location,and train travel speed are analyzed.Through the above study,the law of uneven settlement of the pipe sheet in shield tunnels under different conditions of the underlying soil layer under the action of vibrating train loads is revealed,and the locations where the pipe sheet needs to be focused on are identified,providing an experience for the prevention of shield tunnel diseases.