| With the rapid development of urbanization in China, the development and utilization of underground space also has been increased to the strategic height of human development. Urban subway greatly eases the traffic congestion in cities, air pollution, living space and crisis. The NATM, as a common construction method, based on Rock Mechanics Principle and utilized the self-stability of surrounding rock, holds bolt and shotcrete together as support, and therefore forms a trinity bearing structure composed of bolt, shotcrete and tunnel surrounding rock.Tunnel engineering construction disturbs the stratum inevitably, and generates deformation and movement around. Currently, many domestic and foreign scholars have made a lot of further research about this problem. The large finite element analytic software ABAQUS is adopted to have a simulation on the construction of excavation and primary support based on the first stage construction of215-section of Dalian Metro. The main research contents and conclusion are as follows:(1) The paper concludes the tunnel deformation research situation at home and abroad, summarizes the new Austrian law construction process,measurement technology and construction and monitoring project of the Dalian subway section of215,the paper also introduces the shield law simpily.(2) Through six heart circle of the double hole construction simulation, deformation mainly concentrates in the up section excavation process. When space between two lines was greater than2B (tunnel excavation width), can ignore the influence between construction. After the completion of the excavation, arch feet will produce larger concentration of stress, and the bottom soil produces larger uplift, so Yang arch should be timely done, feet-lock bolt can effectively reduce the stress concentration. The maximum deformation of headroom convergence occurs in the arch feet.(3)The same section of different excavation supporting method simulation and different rock mass of the safety factor method simulation advance that small catheter support more suitable for soft rock. Two-lane tunnel surface subsidence curve of groove "twin peaks" form. Tunnel buried greater than>3D (D for tunnel diameter) will no longer necessary to measure the surface deformation.(4)3D numerical simulation is used in the same cross-section, at the up and down of lining, the stratum deformation reaches maximum, and it decreases along with the distance to the working face increased. The deformation of initial working surface transforms from the sharp deformation stage to slow deformation stage when the excavation face extended forward five excavation steps and the deformation mainly happens at the excavation of the up stage.(5) Through simulation on different thick lining show that lining find that lining not the thicker the better and there is a reasonable value. The main carrying capacity mainly focus on the anchor front-end. Through the release of surrounding rock stress shows that because of the different bearing ability, there is a more reasonable time for primary support. The plastic zone is mainly distributed in the wall, stress and bending moment is also the biggest in the wall.(6) It is adopted to build a2D numerical simulation at the period of excavation and the initial support in three cross-sections located in the deeper, the shallower and the geological poorer area, and a3D simulation of DK35+710section based on the first stage construction of215-section of Dalian Metro. Simulation value and site monitoring data obtain better consistency. |
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