Study On The Mechanism Of Base Void And Deterioration And Damage Of Base Structure Of Heavy-haul Railway Tunnel By Discrete Element Method

Heavy-haul railway will become an important development direction after "highspeed railway" in China because of its advantages of large transport capacity,low transport cost,energy saving,environmental protection and high efficiency.Building Heavy-haul Railway is of great significance to solve the problem of differentiating energy distribution from industrial concentration,optimizing resource allocation and revitalizing local economy.However,with the increase of train axle load and train density,the probability of damage to the basement structure of Heavy-haul Railway Tunnels increases greatly,which has a significant impact on the long-term traffic safety of Heavy-haul Railway tunnels.Based on the two-dimensional particle discrete element method,this paper establishes a single-track Heavy-haul Railway Tunnel model,studies the dynamic response characteristics of the tunnel bottom structure and surrounding rock under Heavy-haul Train load,reproduces the void process and deterioration process of the tunnel basement structure under long-term repeated Heavy-haul Train load,and studies the void deterioration mechanism of the basement structure from the meso-scale.The main research results are as follows:1.Based on the particle flow discrete element method,the interaction model of tunnel surrounding rock under the vibration load of Heavy-haul Train is established,and the dynamic calculation and analysis of the non-void state are carried out.The dynamic response law of train vibration load in the tunnel bottom structure and surrounding rock is studied,and the stress dangerous position of tunnel basement structure and the influence depth of train vibration load in surrounding rock are defined.The dynamic response characteristics of basement structure before and after basement voidage and under different voidage degree are compared and analyzed,and the influence of voidage on the dynamic response of basement structure is proved.2.A simplified model of Heavy-haul Railway Tunnel is established by using twodimensional particle discrete element method.Based on the later stage of repeated loading of long-term heavy-haul train,that is,damage accumulation to medium damage stage,the meso-evolution process of tunnel basement structure and surrounding rock void is reproduced.By monitoring the displacement,pore change and crack development of surrounding rock of the basement,the macro-meso-layer is formed.The mechanism of tunnel basement voidage is explored on the surface,and the effect of basement water enrichment on basement voidage is further analyzed based on the two-dimensional particle discrete element fluid-solid coupling method.3.In view of the inherent defects or acquired diseases of the basement structure,such as unfinished slag,basement void,steel corrosion,etc.,the degradation damage process of the basement structure under the vibration load of Heavy-haul trains is studied from the mesoscopic scale,and the deterioration damage of the normal condition without defects is compared and analyzed,and the influence of the basement defects on the long-term operation safety is proved.According to the basement diseases of Heavy-haul Railway tunnels,the deterioration damage process of the basement structure the disaster-causing mechanism and corresponding improvement measures are put forward in order to provide some reference for the design of Heavy-haul Railway tunnels.