Research on the load condition and dynamic properties for heavy haul railway subgrade

Research purposes: The heavy haul railway is paid extensive attention by countries all over the world because of its large capacity, high efficiency and low cost of transportation. As the most significant part influenced by train loads, the thickness design of the subgrade is usually determined by the principle of the stress ratio of 0.2 between dynamic load produced by train loads and gravity stress of the subgrade itself. While the sharing law analysis of axle force by rail loads on sleepers is the precondition of subgrade dynamic stress calculation, it is essential to analyse the sharing law of train loads and dynamic stress in subgrade. Based on the theory of elasticity finite element model of track-subgrade is established to analyse the load condition under different load levels and subgrade structure, to further solve dynamic stress distribution and attenuation rule in subgrade, which lay a foundation for thickness design of subgrade. Research conclusions:(1)The sharing law of train loads is not effected by the axle loads and the structure of subgrade, train loads are shared by 5 sleepers for single axle wheel, shared by 8 to 9 sleepers for double axle wheels and shared by 15 sleepers for four axle wheels.(2)Wherever the axle load is acted directly above or on any position between the two sleepers, the shape, size and properties of Gauss function curve fited for the loads sharing remain the same, only the position moves as the position of the axle loads.(3)Under single axle wheel the stress ratio between dynamic stress produced by train loads and gravity stress of subgrade is about 0.2 which meet the design principle, while under multi axle wheels the ratio is between 0.3 to 0.5 which does not meet the design principle. (4)The above conclusions have important guiding significance to the structure design of heavy haul railway subgrade. ©, 2015, Editorial Department of Journal of Railway Engineering Society. All right reserved.