Study Of The Classification Of Heavy Haul Railway Tunnel Diseases And Its Influences On Tunnel Safety

As an important form of China's transportation of goods,Heavy-haul railway transportation bears an ever-increasing logistics task.In order to alleviate the increasingly tense transportation demand,the axle load of heavy-haul trains has been increased constantly,which has led to more serious diseases in heavy-load railway tunnels.Based on the theory of linear-elastic fracture mechanics,the stress-intensity factor and stability coefficient of the crack tip of the cracking lining under different surrounding rock environments,locations and depths are calculated by establishing the “load-structure” model of the cracking lining.The stress states of cracked linings under different working conditions have been analyzed and the crack depth has been used as an index to classify the lining cracking diseases.Based on the engineering reliability theory,the probability statistics characteristics of multiple calculated parameters are considered,and a stochastic finite element model of “stratum-structure” that cavities existing behind the tunnel lining has been established in this paper.The calculation of the internal force of tunnel lining and reliability index of different-scale cavities at various locations under different surrounding rock environments are performed.This paper also summarizes the relationship between the location and size of the cavities,the internal force of the lining,and the reliability index.The diseases existing in cavities behind the lining have been graded with the cavity size as an index.This paper applies the measured dynamic pressure of the 30 tons axial-train train as dynamic load,establishes a dynamic finite element model of the tunnel basement and analyzes the dynamic stress response characteristics of the basal-filled layer.Combined with the fatigue failure theory of concrete,it proposes the tension-compression fatigue S-N curve for the tunnel basement filling layer.Through calculation,the fatigue life of basement filling layers with different thicknesses has been obtained.The diseases of insufficient thickness of the filling layer of heavy-haul railway tunnels have been categorized with the thickness of filling layer as an indicator.