Study On Stress State Of Interface Between Sleepers And Ballast Bed Of CRTS ? Double Block Ballastless Track

With the Daxi high-speed rail as the engineering background,for the CRTSI double-block ballastless track,the track-bed plate is a cast-in-place concrete structure,and the double-block sleeper is a prefabricated structure.The old and new concrete Interfaces are easily cracked at the junction.In the actual operation stage,the state of Interface between the double-block ballastless track sleeper and the track bed board will change.Even at the initial stage of operation,the initial damage will be caused by construction factors,affecting the actual force of the ballastless track.This article is based on the theories of temperature field and temperature stress,studied the actual stress of the Interface between the double-block ballastless track sleeper and the track bed board during the construction and maintenance of the track bed and the operation stage of the ballastless track.This is as following:First,based on the basic equations of heat conduction and the finite element method of temperature field,the finite element model was established by using ABAQUS finite element simulation software to simulate the process of pouring and maintenance of CRTSI double block ballastless track beds.Taking into account the hydration heat of track bed releasing heat,the changes of the outside air temperature,the contraction of the concrete in the track bed,and the interaction of the consideration factors,the temperature field and stress field at the interface between the sleeper and the track bed are obtained.The result shows that: only when the heat of hydration is considered,the long-edge surface is subjected to compressive stress in the longitudinal direction of the track,and the short-edge interface is subjected to tensile stress in the transverse direction of the track.When the concrete shrinkage and hydration heat are considered together,because of concrete shrinkage,the long-edge interface is subjected to tensile stress along the longitudinal direction of the track,and the short-edge interface undergoes compressive stress in the transverse direction of the track,which counteracts the tensile-compressive stress generated in the horizontal and vertical directions of the heat of hydration.In addition,it can be concluded that under the conditions of ballast bed pouring temperature and outside air temperature changing,the interface between sleeper and track bed during the construction stage of ballast concrete(pouring and maintaining 28d)will not generate large cracks due to unfavorable forces.Second,the cohesive element was used to simulate the interface between the sleeper and the track bed in the operation period,and the force of the surface between the sleeper and the track bed of the CRTSI double-block ballastless track was studied.The result shows that: under the effect of annual cooling,the long edge of the interface between the track bed and the sleeper is damaged under the normal tensile stress of the interface,and gradually expands to the surface at the corner of the sleeper.Damage occurs under joint shear stress(CSHEAR 2)along the ballastless track longitudinal direction and surface by surface tension stress.The short-edge surface damage is mainly caused by the shear stress along the longitudinal direction of the ballastless track,and the intersection of the interface of the sleeper at the intersection with the long-edge interface is the local CSQUADSCRT.When the value reaches 0.4 or so,the bottom surface of the surface is not damaged,and the interface depth of the surface along the short edge of the interface is gradually reduced.The top damage develops to 60 mm longitudinally from the long edge,and the bottom damage only develops to the sleeper angle.Under the influence of positive temperature gradient at the interface between sleeper and track bed,the main unfavorable areas of the interface under the positive temperature gradient of the interface are four sleeper angles and the middle and upper areas of the long side.The damage of the sleeper angle interface is mainly due to shear.Caused by shear stress.Under the action of negative temperature gradient,the long edge of the surface at the interface is mainly damaged by the normal tensile stress of the interface,and the damage occurs at the entire long edge interface.The damage of the intersection of the sleeper angle occurs at the upper part of the intersection of the sleeper angles.The maximum value of CSQUADSCRT at the interface under loading is 0.29,which is far from the interface failure condition.Through research and analysis of the stress and damage trends of the interface between the sleeper and the track bed in the construction and operation stages,it provides an important basis for optimizing the structure of the double-block ballastless track and operations maintenance.