Research On Nemerical Simulation Of Surrounding Rock-support Structure During Construction Of Large Section For Freeway Tunnels

In the process of tunnel construction, the reliability of surrouding rock and supporting structure is the most important problem we focus on, and more and more researchers pay more attention to this field, it is also the key component of the tunnel construction. On the base of the research results of the previous researchers,a lot of references and experiences were used as an important source in this thesis.According to the Yangzong tunnel and Chaoyangsi tunnel,use MIDAS/GTS finite element software for numerical simulation and summary rock stress deformation characteristics and supporting structure's mechanical characteristics of separate section tunnel deep and shallow small clear space surrounding a large section tunnel's typical class V section with step method,CD method and double side heading method. The main content is list as follows:①The bottom of the vault and the arch rock's pressure less,or even tensile stress;arch foot rock's pressure more after large section tunnel excavation.Small clearance section tunnel by the left and right of tunnel excavation,near the middle rock side of the rock arch have the highest pressure.②Deformation of large section tunnel is more complex than ordinary.Vault and dome uplift subsidence values are larger.The level of deformation of rock of large section tnnel small spacing is more obvious by the excavation of left and right.Change the value of horizontal displacement is not the end and have little effect on the stability of surrounding rock.③Support structure's stress is different between different construction method.It is larger near the middle rock under the construction of large section tunnel small spacing and proposed to strengthen the support intensity here.④Large section tunnel through the numerical calculation,data obtained information that rock and support structures were in normal working condition under different construction method.Double side heading method had the advantage of controling the force and deformation of rock,and it is reasonable large section tunnel construction methods.