Shallow Large Span Of Bias Tunnel Dynamic Construction Of Numerical Simulation And Construction Sequence Comparison And Selection Study

The optimization designs of tunnel section, geometry parameters and load calculation during the constrution of shallow, large-span, unsymmetrically-loaded tunnel, which in different kinds of surrounding rock masses and environment, is a difficult problem in rock and tunnel engineering field, which needs to be solved. Further study of numerical simulation on dynamic construction and constrcution procedure selection of shallow, large-span, unsymmetrically-loaded tunnel has been carried out in this thesis, and some useful results have been gained:(1) Analysis and calculation of the distribution of stress and displacement on different cross-section, i.e. circle, rectangle and ellipse type, during the excavation of large-span single tunnel have been worked out, and the ground pressure in surounding rockmass are disclosed;(2) The concept of 3-D numerical simulation on dynamic tunnel construction is put forward in this thesis. And the calculation principles and the constitutive models of the commonly used 3-D explicit program FLAC^3D are introduced;(3) Numerical simulation of dynamic construction on shallow, large-span, unsymmetrically-loaded tunnel in III, IV, V grade of rock mass have been carried out, and the distribution of the stress and displacement field in different stages during the excavation and the construction of supporting structure have been gained;(4) Comparative analyses on the distribution of the stress and displacement field of the surrounding rockmass and the force condition of the supporting structure in different stages by the "bench method" and the "CD method" during the excavation of the tunnel and the construction of the reinforcement strctures in the shallow, large-span, unsymmetrically-loaded tunnel, and reasonable construction methods and procedures under different kinds of surrounding rock masses are determined;(5) The influences of the unsymmetrical load on the tunnel surrounding rock masses and the reinforcement strctures are anelysed;(6) The concept of dynamic tunnel construction management is put forward along with its points for attention.The research results of this dissertation can be useful to structure design and construction of shallow, large-span, unsymmetrically-loaded tunnels ,it will make the structure and construction of large-span single tunnels be more economic and propery.