Study On Dynamic Response And Fatigue Life Of Bottom Structure Under Disease Conditions In High-speed Railway Tunnel

With the growth of operation time in China's high-speed rail tunnel,various tunnel diseases gradually emerge.The tunnel bottom structure and bedrock are the main bearers of the trainload,so they are the high-risk area for diseases.However,the research on the dynamic response law and fatigue life of the high-speed railway tunnel structure during the service with "disease" is very rare,so there is a lack of reference basis in the process of remediation of tunnel bottom disease.Therefore,the numerical calculation and theoretical analysis method are used to study the dynamic response and fatigue life of the tunnel bottom structure with three disease,including water disaster of basement,layered in filling layer and deterioration of basement under the V-class surrounding rock standard tunnel section and double-line driving.The research contents include the influence of the base water damage on the dynamic response of the tunnel bottom structure,and the general law of the dynamic response of the tunnel bottom structure under the water damage condition;the influence of train load and groundwater on the internal separation of the filling layer,and the dynamic response law during the different lengths of the filling layer separation;the dynamic response of tunnel bottom structure under the bedrock softening and basement void;Fatigue analysis software FE-safe is used to predict fatigue life of tunnel bottom structure under this three kinds of disease conditions.The main results are as follows:(1)When the water disaster occurs in the basement,the groundwater pressure at the tunnel bottom can alleviate the vertical settlement and vibration of the tunnel bottom structure,but the tensile principal stress of the tunnel bottom structure increases significantly,which is not conducive to the long-term stability of the tunnel bottom structure.The damage of the tunnel bottom structure is controled by Tensile strength.The center of the invert arch and the inverting arch directly below the rail are dangerous locations.The vertical displacement,vibration acceleration and principal stress peak of the tunnel bottom structure increase with the increasing of the driving speed.(2)According to the theory of fracture mechanics,the mathematical expressions of train vibration load peak-to-peak value,groundwater pressure and growth rate of internal fatigue crack in filling layer are established.The influence of trainload and groundwater on the internal separation in the filling layer is analyzed.Under the train vibration load,the internal tension area increases accordingly with the increasing length of the internal separation of the filling layer;the vertical displacement and acceleration peak at the upper position of the seam increase sharply,which is much larger than the control index.When the slit penetrates to the edge of the filling layer,and there is located a large tensile stress occurred at the top surface of the filling layer directly above the slit tip,which reaching 75.7%of its tensile strength.(3)When the softening thickness of the bedrock are increaseed,the vertical settlement of the tunnel bottom structure increases,and the vibration acceleration increases first and then decreases,and the tensile stress of the tunnel bottom structure increases obviously.When the width of the substrate is increased,the tensile stress of the tunnel bottom structure increases obviously,and when the space is 3.6 m,the maximum tensile stress at the center of the invert arch reaches 67.5%of its tensile strength,which is unfavorable for the long-term stability of the tunnel bottom structure.(4)When the basement is free from water disaster,the service life of the invert arch meets the design requirements.However,when the driving speed is 300km/h and 350km/h,the service life of the invert arch is 94 years and 76 years,which does not satisfy the design service Years under the water disaster of basement.When the internal seam of the filling layer does not penetrate to the edge of the filling layer,the filling layer structure will not suffer from fatigue damage at 300km/h.When the internal layer of the filling layer penetrates to the edge of the filling layer,the filling layer structure's fatigue life decreases sharply,about 2 years.The service life of invert arch decreases rapidly with the increase of bedrock thickness and base void width,which is far from meeting the design service requirements.