Study On The Effect Of Initial Damage On The Mechanical Properties Of The Bottom Structure Of Railway Tunnel

In recent years,with the rapid development of China's railway construction,the number and total mileage of railway tunnels,as well as the scale and speed of railway tunnel construction has become the world's first.Though great achievements have been obtained in the railway tunnel construction,the railway tunnel service condition is not ideal,and the operating railway tunnel disease problem increasingly prominent,which at the bottom of the tunnel disease incidence is highest.Besides,the service performance of bottom of the railway tunnel structure directly influences train operation safety.However due to this factors such as quality defects and the basal condition change,most of the tunnel service with damage.at bottom of the structure,so it seriously affected the service life of the bottom structure,resulting in damage to the bottom of the problem is prominent.In this paper,aiming at the engineering reality that the disease of the tunnel bottom structure is more prominent,from the bearing capacity and the vibration response characteristics of the bottom structure,the influence of the initial damage on the service performance of the bottom structure of the tunnel is systematically analyzed by means of investigation statistics,theoretical analysis and numerical simulation.And the main research contents are as follows.(1)Based on the investigation and analysis of the typical bottom structure disease engineering examples of railway tunnels in China,from the types of ballast bed,the bottom of the disease,the hydrogeological conditions and the causes of the disease,and so on,this paper analyzes the characteristics and distribution of typical defects in the bottom structure of the tunnel,and summarizes the causes of basal disease.(2)With this condition such as the softening of the basement,the void of the basement,the crack of the bottom structure and the local loose,the bearing capacity of tunnel bottom structure has been analyzed by static limit analysis method.Then the research shows that the influence of substrate softening on the deformation of the bottom structure is more obvious,and the bearing capacity is controlled by the basement deformation.Furthermore,the influence of the basement void on the ultimate bearing capacity of the bottom is more obvious,the bearing performance is controlled by the structural strength.And the effects of cracks and porosity are relatively small.(3)With basal softening,basement concrete pavement,the concrete cracks and partial loose,the vibration characteristics of the bottom structure caused by train vibration has been studied systematically by dynamic numerical analysis method.And the effects of initial damage on the dynamic displacement,vertical acceleration,dynamic stress and stress response of the bottom of the tunnel are analyzed emphatically.Therefore,the research shows that basal condition has the bigger influence on the vibration response,and mainly confined to a certain depth below the base.Next,there is only a single initial crack or local concrete damage,which has little influence on the vibration response of the bottom structure.