Research Of Influence Law On The Base Bed Compactness And Road Bed Under Cyclic Loading Of Heavy Haul Railway

Heavy freight is the development trend of bulk cargo transport. And the large axle load and the long marshalling is the main direction of heavy haul railway development. Increased train axle load can lead to increase intensity and depth of subgrade load, and then causing series of problems of subgrade subsidence and slope satability. Long marshalling trains can make those load continuous effect increase to subgrade and cause intensity of embankment lower and other issues. Meanwhile, with continuous improvement of train speed, the track structure exposed a increasingly serious problem of heavy haul railway. Under the train load repeating effect, these problem mainly is that the rail-subgrade structure generated uneven residual deformation, and then resulting in the track surface unsmooth, finally threatening traffic safety. However, the density, strength and stiffness of the base bed have a close relationship with the generation of subgrade settlement and the rail surface irregularity. Therefore, aiming at these problems, through calculation of numerical and analysis, research the impact and the laws rules of the different nature base bed to the rail-subgrade structure including the road bed and the lower embankment under the train load repeating effect of heavy haul railway.Combined theoretical anslysis, simulation in FLAC3D software and numerical anslysis is the main tesearch method in this paper. Firstly, analyzed theotetically and research the dynamic characteristics of the base bed structure of heavy haul railway. And then put forward related issues the base bed structure faced of heavy haul railway. Secondly, through estblish FLAC3D solid models of heavy haul railway embankment, in the case of the embankment with different stiffness base bed structure, reseach the variation and development process of dynamic stress, dynamic deformation and dynamic sriffness of rail-subgrade structure with the increase in the number of train load effect. Finally, by numerical simulation, summarize their distribution characterisrics and the trends.The main work and conclusions are as follows:First of all, by ANSYS finite element software and FLAC3D software, establish the rail-subgrade system structrure model of heavy haul railway.Secondly, through calculating of static and dynamic train load, there are the maximum unbalanced force curve and dynamic stress and dynamic deformation, and then calculate dynamic stiffness coefficient and analyze the relationships between them.Finally, concluded that:Train static load affects less on deformation of subgrade. Under train static load, there is little effect on base bed compaction coefficient to subgrade deformation. With train dynamic load repeat action, the base bed surface is the position of large changes in dynamic stress. With base bed compaction coefficient K increase, the dynamic stress of base bed and road bed decrease, and when K>0.92, there are small dynamic stress of base bed and road bed, and small rate of change. With the base bed compaction coefficient K increase, the deformation of base bed and road bed decrease, and when K>0.92, their value is small and the rate of change is small. The deformation of road bed increases with increasing base bed deformation, and if K is0.94to0.98,,the deformation is small and the value and the change rate are all small. With train dynamic load repeat action frequency increase, base bed stiffness lower. With the base bed compaction coefficient K increase and train load frequency reduce, the road bed dynamic stiffness coefficient and the base bed dynamic stiffness coefficient decrease. Comprehensive consideration of dynamic stress, dynamic deformation and dynamic stiffness coefficient change, when K is0.94to0.98, there is a good relationship between the base bed and the road bed, and subgrade structure is more stable. Taking into account that the base bed should not only have sufficient stiffness and elasticity, as well as project cost, it is believed that base bed compaction coefficient K=0.96is the optimal matching parameter for the mutual impact between base bed and road bed.