Study On Mechanical Behavior During Large-span Tunneling And Closely-spaced Tunneling Of Multiple Tunnels Region In Metro Station

In this paper,based on the 7th bid section engineering of the Chongqing Rail Transit Line 1 Projects,mechanical behavior during tunneling was investigated through theoretic analysis and nonlinear finite element numerical calculation and site measure,conditioned with the large-span subway station construction and closely-spaced tunneling of multiple tunnels region in metro station.The main research results were obtained as follows:1.The two-dimensional elastic-plastic finite element numerical simulation was conducted to simulate excavation of the large-span subway station and the interval closely-spaced tunnel,which the deformation characteristics and stress distribution of their supporting structure and surrounding rock have been obtained.2.The three-dimensional numerical analysis model was built to analysis tunneling of multiple tunnels region in metro station,with the condition of interval closely-spaced tunneling,which the deformation characteristics and stress distribution of supporting structure and surrounding rock of cross-channel and subway station have been discussed.3.Based on on-site observation test,the construction measure and the investigation of construction technique and construction process have been completed.Which Correcting factor and adjustment of corresponding construction technique were conducted to guide and develop the following tunnel construction through results contrastive analysis between monitoring and numerical simulation.4.It was obtained from the study on the large-span tunneling of subway station with double side drift method,which the maximum value of the stress and deformation is mainly concentrated in the junction between side wall pilot culverts and the springing of pilot culvert.And it was pointed out that the vault settlement increased rapidly after the excavation of the Core rock,which its corresponding vault settlement accounted for more than 60% of the total value.5.It is obtained from the study on the interval closely-spaced tunneling, that the mutual influence during interval closely-spaced tunneling were mainly reflected in the influence on the vertical deformation of completed tunnel caused by the following excavation tunnel's first major excavation. And that the significant variation position of stress and deformation were mainly focus on the junction of the upper and lower and on the tunnel foot arch.6.while the interval tunneling of multiple tunnels region in the large-span metro station,the construction influence to crossing position between cross-channel and subway station was very particular,which will made stress and displacement increase to some extant in the arch initial supporting of subway station.7.Through results contrastive analysis between monitoring and numerical simulation,it's pointed out that the change tendency of corresponding results of stress and deformation was consist basically while there were differences.That the deformation characteristics and stress distribution of supporting structure and surrounding rock could be got and controlled combining monitoring with numerical simulation.