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

After uneven settlement of the roadbed,the CRTS? slab ballastless track will also deform with the settlement of the roadbed.At the operation stage,since the upper part of the base plate is mostly covered with self-compacting concrete and track plate,it is impossible to accurately judge from the surface The crack condition of the base plate,and the crack of the base plate will seriously affect the service life of the entire track structure.Based on this,the thesis establishes a CRTS? slab ballastless track finite element model,and studies the crack initiation of the base plate as follows:(1)The CRTS? ballastless track finite element model is established to analyze the reasons that affect the cracking of the base plate in the operation stage,and find the most important cause of cracking of the base plate.The results show that the uneven settlement of the subgrade is the most important reason for the cracking of the base plate during the operation phase.The single effect of the overall cooling temperature also has a certain effect on the cracking of the base plate small.(2)Establish the finite element model of CRTS? type slab ballastless track in operation stage,mainly consider the subgrade settlement and train load,study the change of the stress field of the base plate under different settlement range,settlement amplitude and settlement position Comparison of tensile strength to determine whether the groove crack and lateral penetration crack of the base plate are initiating.The results show that when the subgrade settlement range is less than 5 m,the base plate groove will not crack.When the settlement range is 10 m ? 40 m,the groove of the base plate may crack,and the cracking situation is the most serious when the settlement range is 20 m.And the groove is easier to crack when the extreme settlement value appears at the joint of the base plate than when it appears in the middle of the base plate.The stress value of each groove increases with the increase of settlement amplitude.The initiation of transverse penetration cracks is consistent with the groove of the base plate.(3)Establish the finite element model of CRTS? type slab ballastless track during operation stage,mainly consider the subgrade settlement,train load and temperature load,and analyze the change of the stress field of the base plate under the effect of different temperature loads,settlement range,settlement amplitude and settlement position Then determine whether there is a crack initiation.The results show that the stress of the groove increases by about 2 MPa when the overall cooling is applied compared to the subgrade and train load,and when the subgrade settlement range is less than 5 m and the maximum settlement occurs in the slab,no crack initiation occurs,when the settlement is maximum The value appears when the crack or settlement range is from 10 m to 40 m,and cracks may appear.After applying a negative temperature gradient load,the groove stress increases by about 1 to 1.5 MPa,and when the subgrade settlement range is less than 5 m,the base plate groove will not crack.When the settlement range is 10 m ? 40 m,the groove of the base plate may crack.The influence of the positive temperature gradient on the crack initiation of the base plate under this condition is negligible.