Study On Deformation Control Method Of Shaly Sandstone Mountain Tunnel Underpass Reservoir

With the rapid development of expressway in China,more and more mountain tunnels have been built in order to shorten the driving distance in mountainous areas,improve the driving conditions in mountainous areas and improve the driving safety.Some mountain tunnels pass through the shaly sandstone area,and the surrounding rock has poor self-stability and strong permeability,so it is easy to soften when it comes to water.In particular,the tunnel under the shaly sandstone tunnel through the reservoir or reservoir brings great uncertainty risk to the tunnel safety construction.Based on the project of Yuchu high-speed Changchongshan tunnel,the finite element software numerical simulation and field monitoring measurement are adopted,Study on deformation,Initial support force and plastic zone characteristics of argillaceous sandstone tunnel when considering fluid-solid coupling effect in different construction methods,The deformation,initial support force and plastic zone characteristics of argillaceous sandstone tunnel without considering fluid-solid coupling effect in different construction methods,The deformation,initial support force and plastic zone characteristics of argillaceous sandstone tunnel under different construction methods and different seepage flow rate are studied,The construction method to control the deformation of surrounding rock and the initial support force is obtained,and the construction plan is optimized according to the actual construction conditions to ensure the construction progress.The main results are as follows:(1)Using the method of numerical simulation of finite element software,For the upper and lower steps reserved core soil excavation method,CD method,bilateral wall pit method three construction methods,Whether to consider the fluid-solid coupling effect,The deformation of surrounding rock,the stress characteristics of initial support and the plastic zone of surrounding rock in argillaceous sandstone geological tunnel are studied,Three construction methods are obtained tunnel surrounding rock deformation,support stress,surrounding rock plastic zone characteristics when fluid-solid coupling effect is considered and when fluid-solid coupling effect is not considered;(2)Numerical simulation of finite element software was used to study the deformation law,initial support stress characteristics and plastic zone of surrounding rock of the tunnel under different seepage flow with three construction methods of reserved core soil excavation method,CD method and double wall guide pit method.Through comparative analysis,it is concluded that in the three construction methods,double-wall guide pit method is adopted to carry out tunnel excavation at different seepage flow rate,so as to minimize the deformation of surrounding rock,minimize the initial support force and minimize the plastic zone.(3)Through the monitoring and comparative analysis of the settlement deformation of the arch and the convergent deformation of the surrounding area of the tunnel in each characteristic section selected from the underground reservoir of changchongshan tunnel,the comparison and analysis of the measured data and numerical simulation data of the on-site monitoring and measurement and the theoretical analysis of the tunnel deformation by the construction method are carried out.It can be seen that the numerical simulation can predict the tunnel deformation caused by tunnel construction in advance,and the deformation of the tunnel can be effectively controlled by strengthening the large deformation section in advance.By using the method of core soil excavation reserved for upper and lower steps,the construction progress can be accelerated.At the same time,the excavation method of upper and lower steps reserved core soil is used to carry out construction.Under the condition of reasonable control of step length and construction sequence,the construction progress can be accelerated,and the deformation of the tunnel can be well controlled.