Research On The Influencing Factors Of Stress And Deformation Of Mountain Tunnels’ Support

Based on a Highway Tunnel,Dongtianshan Tunnel and Xiaoshan Tunnel of Menghua Railway,this paper studies the influence of initial support timing,hardening rate of shotcrete,excavation method and other factors on the stress and deformation of initial support of mountain tunnel by means of literature investigation,numerical simulation and on-site monitoring,and obtains the law of stress and deformation of initial support of mountain tunnel.The main research contents include the following aspects:(1)Research on the deformation law of tunnel initial support under the force of support timing.Based on a Highway Tunnel Project,the time of initial support construction is simulated by setting different displacement release rate of surrounding rock.The influence of initial support construction time on the stress and deformation of initial support is analyzed.The earlier initial support time is,the greater the stress and deformation of support structure is.The rationality of numerical simulation is verified by field monitoring.(2)Research on the influence of hardening rate of shotcrete on the stress and deformation of initial support.Based on the East Tianshan Tunnel Project,by setting the elastic modulus and strength of shotcrete to simulate the hardening rate of shotcrete,the deformation law of initial support under different hardening rate of shotcrete is analyzed,and the conclusion is drawn that the faster the hardening rate of shotcrete is,the larger the deformation of initial support is.The rationality of numerical simulation is verified by field monitoring.(3)Research on the influence of excavation method on the stress and deformation of initial support.Based on the Xiaoshan Tunnel Project of Menghua Railway,the deformation law of initial support under different excavation methods is analyzed by numerical simulation.The results show that the control effect of two-step and three-step excavation methods on initial support deformation is similar,and the rationality of numerical simulation is verified by field monitoring.However,the construction procedure of the three-step construction method is rather complicated,so the two-step excavation method is recommended.