Research On Evaluation Method Of CRTS Ⅲ Prefabricated Slab Track Cracking Condition

CRTS Ⅲ prefabricated slab track is a ballastless track system with completely independent intellectual property rights in China.It has been applied to many high-speed railways in recent years.Field investigations after operation found that with the increase of the speed of high-speed railway trains and the density of trains,and with the actions of dynamic load of the train,temperature load and water pressure,the quality state of ballastless bed deteriorates continuously,and various cracks and damages occur,which seriously affects its durability and service life.In order to guide the maintenance and repair of the line,the relevant departments have revised and improved the maintenance rules for CRTS Ⅲ prefabricated slab track based on the Regulations for High-speed Railway Ballastless Track Line Maintenance.However,the evaluation method to the cracking damage of ballastless track in the rules is still single,and only the provisions of the width of a single crack which exceeds the limit are specified,but the situation of how to evaluate the damage level of the crack is not considered when the width of the crack does not exceed the limit but the number of cracks is large.Thus in order to realize the scientific management of the cracking damage of CRTS Ⅲprefabricated slab track to guide line maintenance more reasonably,a new evaluation index of CRTS Ⅲ prefabricated slab track cracking condition CCI(Ballastless Track Cracking Condition Index)and the relevant calculation method were proposed in this paper.In view of this index,this paper combined two factors,numerical simulation and expert consultation,and used interval analytic hierarchy process to establish the structural hierarchy to determine the weight of each parameter in the index.Through the example verification,the rationality of the evaluation index and the evaluation method were verified.And it has important guiding significance and practical value for line maintenance.The main research contents and conclusions are as follows.(1)Through thorough investigation,six common crack forms on the surface of the ballastless bed have been defined,including transverse cracks,longitudinal cracks,vertical cracks,craquelures,block cracks and through cracks.After studying the application and research status of the quality evaluation index of highway,bridge and culvert,ballastless track,the concept of the evaluation index CCI of CRTS Ⅲ prefabricated slab track was proposed and the calculation method was preliminarily established in the meantime.(2)Based on the basic theory of concrete linear elastic fracture mechanics and the elastic modulus reduction method,the cracking damage analysis of CRTS Ⅲ prefabricated slab track with surface cracks was carried out.And 437 expert questionnaires were obtained by Delphi method,which can fully concentrate on the experience and opinions of experts in practical engineering.(3)In order to ensure the objectivity and rationality of the weights of each parameter in the index,combining the objective analysis of numerical simulation and the subjective opinions of the expert consultation,the interval analytic hierarchy process was used to establish the structural hierarchy to determine the weights of each parameter.(4)The evaluation method was applied to two engineering cases,calculating the CCI with80.68 points and 75.76 points respectively,which verified the rationality of this method.And it can quantitatively analyze the severity of cracking damage of the ballastless bed.Finally,the targeted maintenance suggestions were put forward according to the engineering examples.