Study On The Safety Index Of Shield Tunneling Parameters

With the development of urban subway,the method of shield tunnel is increasingly used in the construction of urban subway.The safety of shield tunnel is very important.How to reasonably control the Shield Tunneling Parameters has become a very concerned problem in tunnel engineering.Based on the shield tunnel project of Fuzhou Metro Line ?,this paper mainly try to find the safety index of Shield Tunneling Parameters by using the method of numerical simulation and Genetic Algorithm.The results can provide suggestions for the similar shield tunnel engineering in the future.The main contents of the studies and achievements are as follows:(1)This paper studies the existing related research results and selects the six Shield Tunneling Parameters which are the main factors influencing the surface subsidence:chamber earth pressure(P1),total thrust(T),torque of cutter head(N),driving speed(v),quantity of grouting(Q),grouting pressure(P2).Studying the influence weights of the six parameters by using the objective multi-factor weight allocation method,which is based on the fuzzy clustering analysis algorithm and the information entropy theory of rough set theory.The chamber earth pressure,grouting pressure and quantity of grouting has great influence on the surface subsidence,the total thrust,torque of cutter head and driving speed has little effect on the surface subsidence.(2)For studying the influence of chamber earth pressure and grouting pressure on the surface subsidence,the FLAC 3D is used to simulate the process of the shield excavation.The original lateral pressure(Ph)and self weight stress of soil(Pv)are calculated by using the theory of soil mechanics.By means of constantly adjusting the chamber earth pressure and grouting pressure,the safety index of chamber earth pressure(P,)and grouting pressure(Pz)are gained.(3)In order to calculate the optimal values of the Shield Tunneling Parameters when the surface subsidence reaches the warning value,the optimization model of Shield Tunneling Parameters based on the Genetic Algorithm is established.The results are compared with the results of numerical simulation,the calculation results are close.Finally,this paper comprehensively consider the results of numerical simulation and Genetic Algorithm,the safety index of the Shield Tunneling Parameters which can be used in Fuzhou Metro project are obtained.