| Under the coupling action of repeated train loads and environmental loads,the slab ballastless track of high-speed railway will inevitably produce various forms of deterioration,damage and diseases,such as interlayer crack,uneven settlement of subgrade,etc.It often has a certain impact on the safety,stability,reliability and durability of the track structure,and even endangers the driving safety in severe cases.Therefore,it is necessary to study the influence law of the interlayer crack of the slab track on the dynamic characteristics of the vehicle-track-subgrade system,determine the evaluation index and limit of the crack damage,and propose the classification standard and control of the crack damage grade to provide theoretical basis and technical support for the maintenance and repair of high-speed railway infrastructure of different speed grades,and it has important theoretical significance and engineering application value.First,this thesis collects relevant domestic and foreign vehicle-track-subgrade coupling system dynamic performance evaluation standards,and preliminarily selects evaluation indicators that may be used for crack damage.At the same time,based on the vehicle-track coupled dynamics theory,the vehicle-track-subgrade coupled dynamic finite element model was established by using ANSYS/LS-DYNA software.The influence law of the slab-end penetration crack and the slab-middle penetration crack on the response of each index of the vehicle-track-subgrade system is simulated and analyzed.And the sensitivity of the response of each index to the crack damage and the possibility of exceeding the limit were evaluated.The research results show that when the CRTS Ⅲ slab ballastless track structure has the slabend penetration crack or the slab-middle penetration crack,the dynamic response of each structural layer of the track will increase to different degrees compared with that without crack.The dynamic response of the track slab has increased more,and the vertical displacement of the slab end has increased by more than 10 times,while the dynamic response of the rail has increased less,and the vertical displacement has increased by no more than 25%.When the vehicle passes through the crack area,the track slab,the self-compacting layer and the base slab will have obvious stress concentration near the interface between the crack and the noncrack,and the stress concentration on the surface of the subgrade is greatly alleviated.The influence of the slab-end penetration crack on the dynamic response of the foundation structure with the same separation size is obviously greater than that of the slab-middle penetration crack.In the evaluation index of the initial separation crack damage,only vertical displacement of the rail,vertical displacement of the track slab and the tensile stress of the track slab is more likely to exceed the limit,so this thesis selects three indexes,such as the vertical displacement of the rail,the vertical displacement of the track slabb and the tensile stress of the track slab,as the evaluation index of the crack damage.Then,this thesis simulates and analyzes the influence of the length and height of the penetration crack and the driving speed on the evaluation index of the crack damage,and calculates the fatigue life of the track slab under different crack sizes.The research results show that the vertical displacement of the rail,the vertical displacement of the end of the track slab,the vertical displacement of the middle of the track slab and the tensile stress of the track slab will increase with the increase of the length or height of the crack,and will exceed its corresponding reference value or maximum allowable value,and the fatigue life of the track slab will also be less than 60 years.The length of the crack and the height of the crack together determine the contact state between the track slab and the self-compacting layer in the crack region.When the track slab is in the unsupported state,the response of each index changes little with the increase of the crack height,and the response is mainly affected by the length of the crack.When the track slab is in the contact state,the response of each index changes little with the increase of the length of the crack,and the response of each index is mainly affected by the height of the crack.The driving speed has little influence on the evaluation indexes of the crack damage.When the vehicle speed is reduced from 350 km/h to 150 km/h,the response of each index is reduced by no more than 26%.However,when the over-limit range of each crack damage evaluation index is not large,the vehicle speed can be reduced to avoid exceeding the limit of each evaluation index of crack damage.It is recommended to control the driving speed below 200 km/h.Finally,based on the influence law of the size and speed of the penetration crack,this thesis discusses the grade limit and classification standard of the crack damage size,and proposes corresponding countermeasures for different grades of crack damage.The research results show that the damage of transverse interlayer penetration crack can be divided into three grades: grade Ⅰ,grade Ⅱ,grade Ⅲ,corresponding to three grades of light,serious and hazardous track structure damage respectively.For grade I damage,the evaluation indicators are all below the reference value,and it is necessary to keep track of the damage status of the track record and follow-up maintenance of the track structure.For grade Ⅱ damage,the evaluation indicators are near the maximum allowable value,and some evaluation indexes slightly exceed the limit.It is necessary to actively formulate a repair plan and repair it in time,and at the same time reduce the vehicle running speed to delay its deterioration development.For grade Ⅲ damage,some evaluation indicators have exceeded the limit significantly,which may endanger the driving safety and require timely maintenance. |
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