Study On Mechanical Properties And Reasonable Type Of Ballasted Track Of Pile-slab Structure In Heavy Haul Railway

Heavy-haul transportation has become an inevitable choice of the world’s countries that can maximize railway benefits because of its excellent properties such as large capacity, low energy consumption, and so on. Embankment of heavy haul railway may have many problems, for example, embankment deformation is too large, post-construction settlement is difficult to meet the requirements. By using pile-slab structure, it could not only meet the deformation requirement of embankment, but also develop the features of high bearing capacity and good adaptive ability. Due to the research and applications in heavy-haul railway ballast track are few, the mechanical mechanism and deformation characteristics are not clear. And based on the results of previous studies, the ballasted bed laying on rigid foundation may exist too large vibration, ballast pulverization, and other issues. Based on this, this paper will mainly study the mechanical properties of pile-slab structure and the reasonable type of ballasted track in heavy haul railway. It will provide theoretical references for the application about the pile-slab structure is used in heavy haul railway ballast track.Based on extensive literature research, this paper generalized research status of pile-slab structure at home and abroad and basic conditions of the disease in heavy haul railway embankment in our country. Directing at heavy axle load and low frequency load characteristics of heavy-haul railway, the thesis proposes the following thinking of research:the numerical model of pile-slab structure is set up respectively under heavy axle load and under low frequency load to study the mechanical properties of pile-slab structure. The principle and method of finite element and attenuation infinite element was introduced in detail and the static and dynamic evaluation indexes will be determined.Static and dynamic mechanical properties of pile-slab structure under heavy axle load that axle load of van is25t were analyzed and also studied the sensitivity of the geometric parameters of pile-slab structure. The results show that the existing structure type of pile-slab structure can meet the the basic requirements for large axle heavy haul train. Pile-slab structure can effectively control the settlement of embankment and improve the stress of embankment that compared with calculation results of ordinary embankment. But the ballast bed vibration is very big because of its larger stiffness and may cause the pulverization of ballast and other issues.The numerical model of pile-slab structure under low frequency load was analyzed by adopting the method combined with finite element and attenuation infinite element to simulate the vertical unlimited extension of the foundation. First of all, the modal analysis was carried out on the pile-slab structure and studied the sensitivity of material parameters and geometric parameters. The results showed that pile-slab structure subgrade in heavy haul railway is low frequency. Secondly, the load transfer law and the influence of different load frequency and amplitude of pile-slab structure under low frequency load were analyzed. The results show that the existing structure type of pile-slab structure can meet the basic requirements for low frequency vibration effect of heavy haul train. But the vibration response will increase and may cause resonance phenomenon when the load frequency close to the natural frequency pile-slab structure embankment.Reasonable type of ballasted track of pile-slab structure in heavy haul railway was studied. The results show that wide sleeper can effectively reduce the stress and acceleration of ballasted bed. The damping effect that adopted scheme of thickening ballasted bed is best compared with scheme of rubber pad under sleeper and mattress under ballast.