Study On Crack Initiation And Propagation In The Base Plate Of CRTS? Ballastless Track For Subgrade Section

CRTSIII ballastless track is affected by hydration heat,ambient temperature,its own structural characteristics and concrete material characteristics,in the construction phase base plate groove angle appear a large number of cracks,so as to affect the CRTSIII type without a frantic jumble orbit long service life.Under this engineering background,the model of CRTSIII ballastless track is established based on the theory of concrete strength and fracture mechanics.The initiation and propagation of groove corner cracks in the base plate are studied as follows:(1)The finite element damaged model of CRTSIII ballastless track was established and to simulate the process of pouring and maintenance of CRTSIII ballastless track base plate.Considering the outside temperature changes,the base plate of concrete hydration heat heat load,concrete shrinkage and negative temperature gradient,the base plate of the temperature field and stress field,at the same time using the stress intensity criterion to judge whether the base plate is cracked or not.The result shows that:when the pouring temperature of the base plate between 12 ?and 18 ?,there will be no cracks in the groove angle of the base plate.Cracks will appear at the groove angle when the pouring temperature is 24 ?.When casting temperature is 30 ?,the longitudinal principal stress of groove angle exceeds the tensile strength of concrete,which leads to destroy.Under the action of concrete shrinkage load,after about 23 days of maintenance,crack may occur at four corners of the longitudinal central groove near the base plate.After 28 days of curing,the negative temperature gradient load is applied.When the pouring temperature is 12 ?,the groove angle of the base plate appears cracks.When pouring temperature is 18 ?,the groove angle produces cracks and extends along the transverse direction to the edge of the plate.When pouring temperature is 24 ?,the surface of the base plate cracks.Finally,when pouring temperature is 30 ?,the whole base plate appears cracks and destroyed.(2)Establishing operation stages CRTSIII ballastless track expansion finite element model,Considering the overall cooling load,negative temperature gradient load and train load,the main factors affecting the groove angle crack and the crack growth of the base plate are analyzed.When the crack depth of the base plate exceeds 5 mm and the crack length exceeds 20 mm,the groove Angle crack of the base plate will cause instability propagation,under the overall cooling load.Negative temperature gradient load and train load have little influence on crack growth,which can be neglected.