Study on the Deformation Law and Construction Optimization of Hard Rock Tunnel in Extremely High Ground Stress
Based on the Baoshan tunnel project of Wuxi-Zhenping expressway in Chongqing,the deformation law and construction optimization of hard rock tunnel without inverted arch under extremely high ground stress are studied by numerical simulation method,and different construction methods and construction steps are compared and selected.The research shows that:1)The deformation laws of tunnels with different construction methods are basically the same.The vertical displacement is greater than the horizontal displacement,and the basement uplift is more obvious than the vault settlement.Deformation convergence of the tunnel constructed by full-section method is the fasetest.2)Different construction methods have the greatest degree of base stress release.After release,the base stress is only 55%of the initial value,and the stress concentration range at the arch foot of the full-section method is the smallest.3)The rock mass around the tunnel is mainly tensile failure,and some parts are shear failure.The horizontal influence range of the construction method on the plastic zone is limited.4)The full section method is feasible and economical for tunnel construction.The basic laws of deformation and stress distribution of different construction steps in the full-section method are the same.The larger the construction step,the greater the horizontal and vertical displacement,the more significant the stress concentration at the arch foot,and the greater the minimum principal stress value.Considering the construction speed,deformation convergence and stress distribution state,it is more economical and reasonable to adopt 1.6 m step.
extra-high ground stresshard rock tunneldeformation lawconstruction methodconstruction optimization
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