| With the acceleration of China’s urbanization process,the underground rail transit in China has entered a period of great development.In the construction of underground rail transit,the subway station has the characteristics of large span,various processes,and the sensitivity of the upper surface to the settlement.Among them,the underground excavation subway station has become a heavy and difficult construction object due to the complicated structural characteristics of the structure during construction,so it is necessary to study the change rule of structure and soil mass in the construction process of subway station in loess stratum.This article based on the somewhere line two metro,Changchengqiao station’s pile-hole excavation method,use static model test box to carry out research on three-arch tunnel excavation encircled by the loess,aimed at the characteristics of the prototype loess,this article successfully configured the model loess,aimed at Irregular section,gypsum tunnel model is successfully perfused,and it meet the requirement of performance index,then carry out the experiments of pile-hole method and middle-hole method,the change process and final value of surface subsidence,lining stress and surrounding rock pressure under different construction methods and different reinforcement conditions are emphatically studied,at the same time numerical simulation analysis on three-arch tunnel excavation method was carried out based on construction example,the effect of stress changes on the structure during the typical construction stage is studied,and the effect of advance reinforcement on strata and surface settlement and restraining the deflection of top longitudinal beam is studied.The following conclusions are obtained.(1)It is concluded that the pile-hole method has some advantages in controlling the surface subsidence and controlling the lining stress.(2)The advance reinforcement has good effect on relieving soil pressure surround arch shoulder and reducing loose soil pressure.(3)These studies have already thrown up the weak position of the three arch lining is located at the bottom of the V groove on secondary lining.(4)The top longitudinal beam may overturning before the arch is done,attention should be paid to the application of temporary steel brace.(5)Advanced reinforcement plays an important role in reducing surface subsidence and ground settlement. |
