Study Of Subgrade Structure Load Transfer Law And Design Method On Heavy Haul Railway Of Large Axle Load

Due to its large capacity,high efficiency,low energy consumption,and low transportation costs,heavy-load railway transportation has received wide attention from countries around the world and has been recognized internationally as the direction of railway bulk cargo transportation.The main means to achieve heavy freight loading are to increase the axle load of freight vehicles,and increasing the axle load can significantly increase the efficiency of railway transportation.However,because of increasing axle load,the rail-subgrade interaction will become more prominent.The increase of the axle load of heavy-load vehicles makes the stress amplitude of the road surface increase significantly.The reduction of the axial distance makes the superposition effect of dynamic stress significant,and the depth of action increases significantly.The increased number of groupings increases the number of continuous actions the subgrade bears.The above effects accelerate the destruction of the subgrade structure,accelerate the development of existing subgrade diseases,cause deterioration of track conditions,and affect the normal use and maintenance of the line.Therefore,the heavy-load railway subgrade structure should have higher bearing capacity,anti-deformation ability and long-term dynamic stability under cyclic loading.In view of the lack of research on the load transfer law and its influencing factors of the heavy-duty railway subgrade structure in China,the single subgrade type structure,the bedrock thickness and the requirements of the filling requirements on the determination of the empirical tendencies are more obvious.The load transfer law and design method of heavy-duty railway subgrade structure under heavy axle load were studied.Based on the theory of vehicle-track-subgrade system dynamics,and on the study of the geometrical dimensions and the mechanical properties of the single-heavy railways in China,the geometrical dimensions of the finite element model are determined,the mechanical parameters of the packing are selected and a single-line heavy-load railway track-subgrade integrated finite element model was established by combining the characteristics of the heavy loads on large shafts.By comparing with the theoretical calculation results,the reliability of the model was verified.Through theoretical calculations and numerical simulation methods,the law of load transfer of track structures was systematically studied.In terms of theoretical calculations,based on the load-sharing Gauss function method,the ratio of sleeper sharing is calculated when a single axis acts directly above the sleeper and between two sleepers.For numerical calculation,based on the single track heavy-load railway track-subgrade integrated finite element model established by the large-scale finite element software ANSYS,the range and size of the wheel-rail forces shared by the sleepers were calculated under single-axis,double-axis and four-axis loads.The effect of different axle weights,orbital parameters(sleeper spacing,fastener stiffness,elastic modulus of track bed)and embankment parameters(bed surface elastic modulus,bed bottom elastic modulus,foundation elastic modulus)on the load sharing ratio of sleeper under uniaxial loading was analyzed.Based on the single-line heavy-load railway track-subgrade integration finite element model,the dynamic stress of each layer of the subgrade structure was calculated.The distribution of internal stress along the transverse and longitudinal directions and the vertical attenuation law of the subgrade structure are analyzed.The influences of different axle weights,orbital parameters(fastness of fasteners,elastic modulus of track bed),subgrade parameters(substrate bed modulus of elasticity,base bed elastic modulus,elastic modulus of foundation)on dynamic stress distribution characteristics were discussed.The energy dissipation mechanism of the subgrade structure was revealed.In order to control the long-term cumulative deformation of the heavily loaded railway subgrade structure,the gradual deformation state of the deformation is controlled with the action of the major axis.Based on the characteristics of large-scale heavy-load train loads,the control criteria and calculation methods for the subgrade design of heavy-duty railways under heavy-axis re-strength with three factors of dynamic strength,support stiffness and long-term stability are established.Combined with the requirements for the design of the foundation bed in the "Code for heavy-haul railway design"(TB10625-2017),two proposed schemes are proposed for the foundation bed structure under heavy loads of 45 t.The research results will provide theoretical guidance for the development of China's heavy-load railways.