Dynamic Influence And Identification Of Mortar Gap Damage Of CRTS Ⅱ Slab Ballastless Track In High Speed Railway

Ballastless track has characteristics of high smoothness,high stability and small maintenance.So it is widely used in the construction of high-speed railway in China.However,with the accumulation of high-speed railway operation mileage,there are many operation problems in ballastless track.One of the problems is that the mortar layer gap.After the gap damage between the track slab and the mortar layer,when the train passes,the mortar layer in the gap area will no longer contact with the track plate and will be in a void state.The way of bearing and transmitting force of track structure is also changed.Therefore,the vibration of wheel-rail system will be intensified.How to identify and master the damage of mortar gap and the degree of damage quickly and accurately.This is of great significance to the service performance evaluation and maintenance management of ballastless track structure of highspeed railway.Therefore,in this thesis,the CRTS Ⅱ slab ballastless track of high-speed railway was selected as research object.The law of the initiation and expansion of the mortar layer and the dynamic influence of mortar seam damages on the high-speed vehicle-rail coupled system were analyzed.On this basis,the research on the damage identification of the off-line joint was carried out.The main work and research results are as follows(1)The finite element model of CRTS Ⅱ slab ballastless track including the cohesive zone model was established.The influence of positive and negative temperature gradient loads on the initiation and development of the mortar layer was analyzed.The difference between the two kinds of temperature gradient loads on interlayer damage was compared.The influence of the mortar layer stiffness on the damage propagation of the gap under temperature gradient loads was studied.And the influence of plus-minu temperature gradient load on the track structure deformations was also analyzed.The results show that the damage areas and track structure deformations of CRTS Ⅱ slab ballastless track increase with the increase of temperature loads.The negative temperature gradient load has more serious influence than the positive one at the same values.It has little effect on the interlayer damage when the temperature gradient loads are-10 ℃/m～20 ℃/m.The higher the mortar layer stiffness,the more serious interlayer damage caused by the same temperature load.The end seam is mainly controlled by the normal stress and the transverse shear stress,while the edge seam is mainly controlled by the normal and longitudinal shear stress.Under the same temperature gradient load,the deformation of the track plate is greater than that of the mortar layer.Under the positive temperature gradient,the deformation of the track structure along the edge of the slab is greater than that along the middle of the slab.While,under the negative temperature gradient,the difference between the two is not significant.(2)Based on the vehicle-track coupled dynamic theory,vehicle-CRTS Ⅱ slab ballastless track coupled dynamics model was established.The damage of mortar layer was considered in the model.The dynamic response characteristics of the vehicle and track system under the condition of different interlayer gap damages were analyzed.The dynamic effect of operation speed in the damage area of the gap was discussed.The results show that the vibration responses of the high-speed vehicle-track system are less affected by the single gap debonding.When the height of the upper arch of the track slab from the joint area is more than 1mm,the vertical wheel-rail force,the vibration accelerations of wheel set and rail and other indexes increase significantly,the rail vibrations are particularly severe.While the vertical acceleration of the car body changes relatively little.When the vehicle speed is lower than 200 km/h,the gap damage mainly affects the vibration of the track structures.It has little influence on the operation comfort and safety indexes.When the vehicle speed is higher than 300km/h,the vertical wheel-rail interactions are aggravated,and the running quality of high-speed vehicle is deteriorated.(3)Based on the neural network theory,a BP neural network model was established for the identification of the damage of the gap.The rail vertical acceleration index,which is the most sensitive to the damage of the gap,was selected as the input of the neural network system.The recognition results of BP neural network system for damage and damage location under single and double damage conditions were analyzed.The recognition effect of BP neural network system on the gap damage degree was studied.The results show that the established BP neural network model can identify and locate the gap damage and judge the extent of the damage.Compared with the single damage condition,the double damage condition is more complex,and needs more training times to iterate to the allowable error range.The actual output error will increase relatively,but all of them are within the allowable error range.