Research On Stability And Reinforcement Of Mountain Tunnel Under The Effect Of Fluid-solid Coupling

In recent years,the focus of high-speed railway construction has continuously shifted to the Midwest regions.There are many mountains and rivers in the Midwest regions.During the construction of the tunnel,it is inevitable to pass through the waterrich section or even the water-rich fault fracture zone and virous tunnel accidents such as large deformation,landslide,mud and water inrush are easy to happen due to the fluid-solid coupling of groundwater.In order to ensure the safety of the construction of the mountain tunnel with rich water,this thesis relies on the Jianping Tunnel,and uses theoretical derivation and numerical simulation to study the stability and reinforcement measures of the mountain tunnel with rich water under the effect of fluid-solid coupling.The main research content and results include:(1)Based on the three-dimensional nonlinear GZZ yield criterion,the elastoplastic solution of a deep-buried circular tunnel under the effect of seepage considering the intermediate principal stress is derived.Use the finite difference calculation program written in Python to analyze the influence of the intermediate principal stress,seepage force and supporting force on the stress field,displacement field and plastic zone of surrounding rock.The results show that the intermediate principal stress is useful to improve the stability of the surrounding rock,the increasement of seepage force will reduce the stability of the surrounding rock,the support force can effectively control the deformation of the surrounding rock,but it is necessary to implement advanced support to meet the deformation control requirements,when the seepage force is large.(2)Aiming at the defect of theoretical analysis,the FLAC3 D complete fluid-solid coupling analysis is used to simulate the three-step temporary inverted arch excavation method,to analyze the influence of different initial water levels on the seepage field,displacement field,plastic zone,and support stress,and determine the weak location of the tunnel under high water level.The results show that the groundwater flow rate is the fastest at the arch foot position,and the pore pressure behind the primary support at this location is the largest,so it is necessary to strengthen the waterproof and drainage measures.The arch bottom of the tunnel is most sensitive to the change of the initial water level.When the initial water level is high,the increasement of plastic zone and deformation of the surrounding rock at the arch bottom is the most.The maximum tensile stress appears on the inner side of the invert arch,and the tunnel is prone to happen bottom heave failure.(3)Use numerical simulation to analyze the influence of grouting circle parameters on the seepage field,displacement field,plastic zone,and support stress,and determine the optimal grouting parameters.The grouting circle effectively shares the pore pressure and improves the mechanical properties of the surrounding rock.The increasement of the permeability coefficient ratio and the grouting cycle thickness are helpful to improve the effect of waterproof and reinforcement.The optimal grouting circle permeability coefficient ratio is 50,and the optimal grouting circle thickness is 5m,(4)Use numerical simulation to analyze the influence of the oblique fault fracture zone with rich water on the seepage field,displacement field,plastic zone,and support stress.The effect of the reinforcement scheme in the fracture zone is evaluated based on the measured data.The results show that the stability of the tunnel in the fracture zone is significantly reduced.Affected by the spatial position of the fracture zone,the seepage field,displacement field,plastic zone and stress of the supporting structure in the fracture zone all show asymmetry.When only the initial support is applied,the tunnel face collapses and the bottom heave damage occurs.The use of advanced curtain grouting,advanced small pipes,and mortar bolts combined reinforcement scheme can improve the safety of the tunnel through the oblique fault fracture zone.