Damage Behavior Analysis For The Sleeper's Joint Surface Of Double Block Ballastless Track

As one of the representatives of the advanced ballastless track structure in the world,CRTS? double block ballastless track with strong adaptability,mature technology and relatively low construction cost is successfully applied in China.However,debonding and cracks can be easily formed on the joint surface of the sleeper due to the different construction sequence and the poor overall integrity of this track structure,which calls for urgent attention.Based on the disease research of the double block ballastless track investigated on site and the principle of inter-layer and interface damage coupling,the damage behavior at the joint surface of the sleeper was studied using the concrete damaged plasticity model and cohesive zone model.First of all,through the field research of the double block ballastless track in Suining to Chongqing railway,the main damage forms were summarized and classified,meanwhile,the characteristics and cause of the inter-layer damage at the the joint surface of the sleeper were analyzed.Secondly,through the concrete damage plastic and cohesion zone model in finite element software,the spatial detail calculation model of the CRTS ?double block ballastless track was established on the principle of inter-layer and interface damage coupling.The inter-layer and interface damage behaviors and the stress state of the joint surface of the sleeper under the axial temperature and temperature gradient were studied.The results show that excessive inter-layer stress can lead to tension and shear damage on the joint surface,and the damage will become more serious with the temperature increasing.When temperature increases,the damage zone is mainly concentrated on the bottom part,otherwise,on the surrounding part.For the concrete slab,when temperature decreases,tensile damage tends to appear on the long side part.As the drop of temperature increases,the damage will extend to the surface of the concrete slab and finally coalesce.Finally,based on the damage coupling model,the influence of train loads on the inter-layer and interface damage behaviors and the stress state were analyzed when there existed initial damage caused by side debonding and temperature gradient cycling.It can be found that when there is side debonding between the layers,the damage zone between the layers increases obviously,but when the debonding area reaches 50%,the damage zone is basically stable and will not develop anymore;under the dynamic train load,the inter-layer damage will aggravate the overall integrity of the track structure.For those track structure with inter-layer damage,the vertical displacements of the sleeper block and the concrete slab have increased by 0.56% and 10.89% respectively compared with those have no inter-layer damage;the vertical acceleration have increased by 1.40% and 11.89%,respectively.And the effect under the passenger train is slightly significantly than under the freight train.As the temperature gradient amplitude alternates,the concrete slab appears tensile damage accompanied with stiffness recovery phenomenon.