Study On The Optimization Of The Structure Of Heavy Haul Railway Subgrade

In the field of coal mineral transportion, heavy haul railway is favored by the majority of developed countries, which is characterized by low transportation cost, high efficiency and strong transport capacity. However, subgrade will cause different degrees of disease due to the large axle load. At present, the domestic heavy haul railway has similar problems of roadbed disease that will leads to the formation of railway safety hazards and economic losses. Therefore, it is important to study the rationality of the subgrade structure of heavy haul railway for the railway maintenance, operation safety and economic benefit.The paper as the engineering of ZhangTang heavy haul railway as the research background, in the construction process, the monitoring and summary regular were implemented on the internal stress and displacement of the subgrade, and combined with soil arching causes to analysis subgrade settlement. The research indicates that the construction settlement mainly occurred in the process of compacted upper subgrade soil range within 5 m, and the settlement rate plunged and tends to be steady when soil over 5 m. The amplitude of stress and displacement has the similarity in the same layer that indicate each layer of bed structure has uniform stiffness. In the subgrade construction process, the complexity of soil arching shows that soil arching is not simple two feet arch in the plane, but multi foot arch in space like shell structure.To study the subgrade stiffness matching and load transfer regularity by accessing to relevant references and using Kentrack finite element software, and obtained stress level of subgrade structure layers under the axle load 30 t and 32 t respectively. And the optimization of subgrade under 30 t axle load is based on satisfying the bearing capacity and the design service life requirements, the improved bed thickness is 3.0 m, the subballast is 0.5 m and subgrade is 2.5 m. The analysis also illustrates the ballast thickness and rigidity play an important role in the transmission of upper load, the results show that the subballast surface compressive stress decreases rapidly with increasing thickness of the ballast. And suggest the thickness of ballast under 30 t axle load should not be less than 0.5 m.Under the precondition of ensuring strength requirements and the design life, the bed structure of The Combination Trackbed under the 30 t axle load was optimized and calculated, and get the total design thickness of bed structure is 2.6 m, including asphalt layer of 0.1 m, the subballast layer 0.5 m, the subgrade layer 2.0 m. This reduces 0.4 m based on the design of bed with a thickness of 3 m. And suggest the thickness of ballast under 30 t axle load should not be less than 0.3 m.