Study On Disease Assessment Method Of CA Mortar Layer Of CRTS Ⅰ Slab Track On Bridge Based On Dynamic Stiffness Index

CRTSⅠ slab ballastless track is one of the key ballastless track structures in China’s passenger dedicated line.The CA mortar layer filled between the track slab and the base slab has the characteristics of low elastic modulus,low strength and high tougliness.It is an important force transfer and buffer structure of ballastless track structure.In the course of service,diseases,such as deterioration and debonding appear in CA mortar layer,directly affect the durability of track structure and the smoothness of train operation.However,there are few studies on the assessment methods of typical diseases of CA mortar layer.Based on CRTSⅠ slab ballastless track on simply supported girder bridge,the causes of typical diseases of C A mortar layer and its influence on dynamic response are analyzed,and the method of disease assessment is further proposed.The main research works and conclusions are as follows:(1)The warping deformation and stress law of track structure under temperature gradient are studiedA simplified static analysis model of CRTSⅠ slab ballastless track is established.Taking maximum temperature gradient as load,the deformation and stress characteristics of track structure under three kinds of constraints are compared and analyzed,including single restraint of dead weight,joint restraint of dead weight,rail and fastener,and joint action of dead weight and train load.At the same time,the relationship between the magnitude of temperature gradient and the mechanical properties of track structure is discussed.On this basis,the vulnerable areas of deterioration,fracture and debonding of CA mortar layer under slab are preliminarily determined.(2)The influence of deterioration and debonding of CA mortar layer on dynamic responses of the bridge and track structure are analyzedBased on the dynamic analysis model of CRTSⅠ slab ballastless track on bridge,the dynamic responses of the bridge and track structure under disease-free condition are analyzed.From the point of view of the disease of CA mortar layer,the influence of some parameters on the dynamic response of bridge and ballastless track are studied,including the elastic modulus,void location and void length of CA mortar layer.(3)A method for disease assessment of CA mortar layer based on dynamic stiffness is proposedTaking the impact response of track slab as input,the variability index of dynamic stiffness is used to construct the assessment index,and the preliminary positioning and refined assessment of CA mortar layer diseases are carried out.At the same time,the influence of disease area and extent on the assessment results is discussed.Finally,the corresponding evaluation criteria and evaluation process were summarized.Taking ballastless track on Harbin-Dalian High-speed Railway Bridge as the experimental object,the impact test is carried out in typical disease section,to verify the reliability and validity of the assessment method in this paper.