Analysis Of The Interface Damage Of CRTSⅡ Slab Track Under Sustained High Temperature

Along with the high-speed railway entered into the phase of operation and maintenance,all kinds of structural damages begin growing caused by the degradation of track structure performance day by day.Among them,the interface damage between the track slab and CA mortar is one of the most typical diseases of CRTSⅡ slab track system.According to the site investigation of operation line,the interface damage between CRTSⅡ slab and mortar layer frequently occurs during the sustained high temperature in Summer,whereas CA mortar layer is the key structural layer of track structure which can bear and transfer force,the interface damage could lead to deterioration on the carrying capacity and have an impact on the durability of track structure.Based on the existed research,the interface damage of CRTSⅡ slab track under the sustained high temperature is studied.The main contents are as follows:(1)The temperature field trial of CRTSⅡ slab in Eastern China.According to the site investigation of operation line of the high-speed railway in Eastern China,it analyzes the distributed and function characteristics of typical structure damages.And the temperature field monitoring section of CRTSⅡ slab was established in typical damages area by independent research and development on-line monitoring system,which can monitor the temperature field of track and meteorological parameter around this track.(2)The monitoring data analysis of CRTSⅡ slab on roadbed temperature and meteorological parameters.Based on the temperature field trial of CRTSⅡ slab in Eastern China,the distribution and time-variant characters of the track temperature in different depth and slab temperature gradient variation were analyzed by mathematical statistics method.Among them,the characters of slab temperature and temperature gradient variation during sustained high temperature are the emphasis.Studies have shown that,the temperature of slab each layer retains above 30℃ and the maximum positive temperature gradient of slab greater than 60℃/m under sustained high temperature function,and the curve of vertical temperature load mode of slab presents exponential distribution regularity.(3)The relevant characters analysis of interface damage under sustained high temperature effect.According the characters of CRTSⅡ slab track structure,a spatial solid finite element model was established,including cohesion interface elements to simulate the behavior of damage development between slab and mortar layer.By imposing the practical positive temperature gradient load of slab during sustained high temperature on the finite element model,the mechanical characters of track structure and development characters of interface damage were analyzed.Studies have shown that,although the slab maximum positive temperature gradient has not exceeded the code standard,the sustained effect of positive temperature gradient results in debonding between slab and mortar layer and interface damage emergence.The greater positive temperature gradient and the longer sustained effect,the larger interface damage area and the worse interface damage degree.And the interface damage development during sustained high temperature function can be divided into three phases:incomplete damage generation、incomplete damage transform into complete debonding、complete debonding aggravation.Based on the characters of interface damage development and trial data,maintenance suggestions of interface damage for different phase were proposed.