Research On Unlocking And Relocking Safety Of CRTSⅡ Slab Ballastless Track Unitization

CRTSⅡ slab ballastless track has been used in our country for more than ten years.Due to the vastness of our country and the large temperature difference between the north and the south,CRTSⅡ slab ballastless track has always been subjected to complex temperature effects.There is a large longitudinal temperature force between the track slabs,and high temperature expansion in summer has become a common phenomenon.Unitization is the most direct way to solve the expansion of the track plate and release the longitudinal temperature force of the track plate.In order to ensure that the CRTSⅡslab ballastless track can safely transform from the existing state to the unitized state,the force and deformation of the seamless track and ballastless track are controlled within a reasonable range,this thesis focuses on the study of the stress and deformation laws of the seamless track and ballastless track structure when the CRTSⅡ slab ballastless track is unitized at the bridge and subgrade,analyzes whether the CRTSⅡslab ballastless track is safe when it is unitized,and propose reasonable unlocking and relocking conditions and technical requirements for track slab unlocking construction.The main work content is as follows:(1)A finite element model of CRTSⅡ slab ballastless track of bridge section and subgrade was established,under different unitization schemes of bridges and subgrades,study the law of force and deformation of the ballastless track during unlocking and relocking,and put forward the technical requirements for the safety of track structure in unlocking and relocking.(2)Analyse the force and deformation law of unlocking and relocking the bridge and subgrade track structure.The influences of different temperatures,different bonding conditions between the track slab and CA mortar layer,whether the fastener is released,whether the bar is planted at the unlocking position,and the elastic modulus of different filling materials between the joints during relocking on the mechanical deformation of the track structure are analyzed.Judge whether the stress and deformation of the track structure is within a reasonable range when the bridge and subgrade is unitized.The analyse results show that the stress and deformation of the track structure on the subgrade is much smaller than that of the bridge,when the bridge is unlocked,the difference between the temperature of the track slab and the locking plate is ±5 ℃,and the force and deformation of the track structure are within a safe range.When the road base section is unlocked,the difference between the temperature of the track plate and the lock plate is between-5 and 10 ℃,When the bridge and subgrade are unlocked again,the temperature of the track slab is 5 ℃ and 10 ℃ higher than the temperature of the locked slab respectively,and it is safe to relock.(3)Using theoretical simulation and on-site track slab unlocking experiments,analyze the stress and deformation of the track structure during the unlocking and relocking process of the reinforced section and the unreinforced section,putting forward the key technical requirements of the track slab unlocking construction.