Research And Development Of Steel Sleeper With Automatic Settlement Compensation On Transition Sections And Analysis Of Its Mechanical Characteristics

With the rapid development of railway in china,the transition problem between different structures on railway lines has become more and more concerned.And the foundation settlement on railway lines has become a key constraint factor for the sustainable development of high-speed railway,especially the differential settlement on the railway transitional area,which has become one of the important factors affecting the smooth,comfortable and safe driving about high-speed train.Therefore,it is of great engineering significance to study the remediation technology of foundation settlement under rail on transition sections.First,the paper collected domestic and foreign research data on the remediation technology of foundation settlement under rail on transition sections.Based on the comprehensive analysis of the current research situation,the paper developed a new kind of steel sleeper for compensation settlement automatically according to the characteristics of the superstructure's subsidence that caused by foundation settlement under the railway transition sections,and the function reliability of the automatic compensation settlement about the steel sleeper was verified by laboratory tests.Second,based on the finite element method,the space finite element model of new steel sleeper was established,and the relevant structural parameters were optimized based on the structural strength analysis.Then,based on the ordinary ballasted track structure,the space finite element models of steel sleeper and concrete sleeper track-subgrade were established,and the mechanical properties of the both track structures were compared and analyzed.Finally,the influence of key structural parameters on the mechanical properties about the steel sleeper track structure was studied.The main research work and results of the paper are as follows:(1)Based on the existing concrete sleeper structure,the paper developed a new kind of steel sleeper,which could realize the function of automatic settlement compensation on railway transition sections.And the structural characteristics and working principle of the steel sleeper were introduced in detail.On this basis,the structural strength of settlement compensation device in steel sleeper was checked and it verified the reliability of the automatic compensation function of steel sleeper through laboratory tests.The results show that the compressive strength,shearing,yielding and fatigue strength of the settlement compensation device in new steel sleeper meet the requirements under train load.The steel sleeper can realize the automatic settlement compensation under the condition that foundation settlement under rail is happened.(2)The three-dimensional model of the steel sleeper was established by using the finite element software ANSYS.Based on the structural strength analysis,the relevant structural parameters were optimized,and the reasonable values of structural parameters about steel sleeper were selected.The results show that the lateral compressive stress of the overall sleeper and the stress in all directions at the serrated structure increase with the increase of settlement compensation.The strength in all directions of steel sleeper can meet the requirement under certain amount of settlement compensation.Increasing the width of the steel sleeper can reduce the lateral compressive stress of the overall sleeper and the stress in all directions at the serrated structure,and it is recommended that the width of the steel sleeper should be 32cm~34cm.When the steel sleeper's top thickness is greater than 3cm,the lateral compressive stress of the sleeper exceeds the strength limit,and it is recommended that the thickness of steel sleeper's top should be 1cm~3cm.The height and bottom thickness of the steel sleeper have little effect on the strength of the overall steel sleeper and steel sleeper's serrate structure.The thickness of the steel sleeper's side plate has obvious influence on the lateral compressive strength of the overall steel sleeper and the strength in all directions at the serrated structure,and it is suggested that the thickness of the steel sleeper's side plate should be 2cm~4cm.(3)The paper has established a vehicle-rail coupling model,through which it calculates the vertical wheel-rail force.According to the ordinary ballasted track structure on existing lines,the space finite element models of steel sleeper and concrete sleeper track-subgrade were established respectively by applying the maximum value of the vertical wheel-rail force,and mechanical properties of the both track structures were compared and analyzed.The results show that the new steel sleeper track is superior to the traditional concrete sleeper track in resisting deformation and bending resistance.In general,the difference in the mechanical characteristics of the sleeper between the both track structures is the largest,the rail and track bed are the second,the subgrade is the smallest.With the increase of settlement compensation amount,the stress of the steel sleeper structure decreases,but the bending moment of the rail and the positive bending moment of the steel sleeper increase.Therefore,the settlement compensation amount of the steel sleeper should be within a reasonable range.(4)Based on the established finite element model of steel sleeper track-subgrade space,the influence of key parameters such as rail pad stiffness,steel sleeper spacing and elastic modulus about ballast bed on the mechanical properties of steel sleeper track structure was studied.The results show that the stress and deformation of the rail are reduced with the increase of the rail pad stiffness in the steel sleeper,but the stress and deformation of the steel sleeper,ballast bed and subgrade are increased.Reducing the spacing of the steel sleeper can help reduce the stress and deformation of the track structure,but too small spacing of steel sleeper will increase the difficulty of tamping the railway ballast,and increase the maintenance workload and costs.Increasing the elastic modulus of the ballast bed can help reduce the deformation of the track structure,but at the same time it will increase the force of the steel sleeper and the ballast bed.It is recommended that the orbital parameters such as rail pad stiffness?the steel sleeper spacing and elastic modulus of ballast bed should be chosen rationally after comprehensive consideration.