Study On The Excavation-induced Deformation And Settlement Of Shallow-buried Subway Tunnel In Loess Area

With the rapid development of urban railway transportation, the construction of subway also develops rapidly. Nowadays, the shallow-buried excavation method commonly is used to the urban subway construction. During excavation of subway, the surrounding displacement of tunnel and settlement of ground often is caused, and the deformation of tunnel structure also is affected by traffic loading on ground. However,the study of effect of traffic loading on subway construction at loess area is relatively rare. In this paper, based on the engineering of Metro line 4 between Feitian road and Hangtian avenue in Xi’an, the excavation-induced deformation and settlement of shallow-buried subway tunnel at loess area will be studied by the numerical simulation and monitoring data. The main study resutls are as follows:Monitoring data of the ground settlement, vault settlement, horizontal convergence and surround rock pressure are obtained during the construction. Effects of tunnel excavation on the surrounding environment are analyzed.Using the ANSYS finite element software, numerical model of double-line parallel subway tunnel is established, the effects of tunnel excavation on surface settlement, initial supporting and buried pipelines influence are studied. Rationality of results of numerical simulation is verified by the monitoring data. The research results show that vault settlement, initial support principal stress both are larger on the entrance of the tunnel than other section of the tunnel. Thus, the location of tunnel entrance will be mainly researched in the dynamic analysis.According to the practical engineering, the vibration response of initial support at the tunnel entrance is analyzed by using the transient analysis. Vibration response of initial support under different vehicle speed and load are studied under single and double line ground road. The results show that the most disadvantaged effect of vehicle load on the support structure is caused under double line road and the same driving direction. Besides, vibration response of support structure is also relatively large at the intersection of vehicles. These research results provide the certain reference to evaluate the effect of vehicle load on the structure of the underground tunnel and improve the design theory of subway tunnel structure.