Study On Interface Characteristics Between Asphalt Concrete And Base Plate Of Ballastless Track

As the key components to connect the ballastless substructure,interface characteristics of the foundation bed plays an important role in ensuring long-term service performance of high-speed railway.In order to meet the requirements of longterm stability and settlement deformation of the high-speed railway,it is necessary to satisfy the dynamic characteristics of the wheel-rail system and to ensure the long-term stability and interface safety of the infrastructure under repeated dynamic and environment loads.Based on the field test project,this paper studied the interface characteristics between the asphalt concrete substructure and base plate of the ballastless track.Through conducted the strength test between the composite interface,the characteristics of interlayer interface damage and its influencing factors were summarized,and the interlayer interface parameters were obtained based on the principle of time-temperature equivalence.Meanwhile,the bilinear cohesion model can better describe the interlayer mechanical behavior between asphalt concrete substructure and base plate was shown based on the full-scale field test results,.Based on the bilinear cohesive model,the paper analyzed the evolution process of interfacial characteristics between asphalt concrete layer and base plate under temperature load and discussed the effects of whole temperature and temperature gradient on interfacial bonding performance.Then the dynamic analysis model of crack foundation which considering the couple effect of temperature load and interlayer damage are established in this paper.It analyzed the propagation and evolution of interlayer damage under the train load,and studied the influence of the bonding state between asphalt concrete layer and base plate on characteristics of ballastless track.The main conclusions were as follows:1)Under the load of whole temperature,the interfacial shear stress at the seam of the base plate first reached the shear strength,which leaded to the initiation of microcracks.With the increase of temperature,the interfacial micro-cracks propagated and the interface de-bonding occurred,which leaded the interfacial state changed from bonding state to contact friction state.Increasing the interfacial shear strength and fracture energy parameters can effectively reduce the area of de-bonding zone and excessive interfacial stiffness will lead to the damage earlier.2)Under the load of the temperature gradient,the micro-cracks only initiated near the seam of the base plate.With the normal range of service,there will be no de-bonding failure of interlayer interface under temperature load.3)Most of the interlayer damage was still dominated by the temperature load,and the damage seldom propagated under the train load separated.The influence on wheelrail dynamic characteristics was small when the bonding state changed without complete de-bonding,and it was greatly affected by the transition from full de-bonding to contact friction.4)In order to ensure sufficient strength between the asphalt concrete layer and base plate,in this study,the safety performance required the interfacial shear strength should not less than 0.6MPa when the loading rate is 5mm/min under the temperature of 25℃,and the bonding strength should not less than 0.3MPa when the loading rate is 30mm/min under the temperature of 25℃.