Performance Evolution And Numerical Calculation Of Filling Layer SCC With Macroscopic Crack Under Freeze-thaw Cycle

Self-compacting concrete(SCC)filling layer is the core component of CTRS Ⅲ slab track,which has an important influence on the stability and durability of the track structure.Due to reasons such as construction,environment,load and material,vertical cracks will appear on the outer side of the SCC of some filling layer,and the cracks will expand during service,which is unfavorable to the track structure.Based on this,this paper studies the changes of the SCC properties of the filling layer with macroscopic cracks under freezing and thawing and the evolution of cracks,and calculates and analyzes the influence of the combined action of environment and load on the filling layer performance through finite element software,in order to further grasp the performance of the filling.The long-term service performance of the structure provides experimental and theoretical basis.The main research contents and results of the paper are as follows:(1)The propagation evolution of SCC macro-cracks under repeated loading and its effect on SCC performance were studied.Repeated loading leads to stress concentration at both ends of the macroscopic crack,the crack expands and extends along the length direction,and the crack width increases,but the depth does not change significantly.The existence of macroscopic cracks leads to a decrease in the elastic modulus and mechanical properties of SCC.(2)The evolution of the properties of SCC with macro-fractures and the evolution of macro-fractures under freeze-thaw were studied,and the damage constitutive model of SCC with macro-fractures under freeze-thaw was established.Cracks reduce the SCC elastic and dynamic moduli and significantly increase the SCC degradation rate.In the SCC damage constitutive model,due to the presence of macroscopic cracks,the distribution parameter an increase exponentially and the shape parameter b decreases exponentially,resulting in a substantial increase in the peak strain of the material and a decrease in brittleness and stiffness.The freezethaw damage rate of the cracked SCC is higher than that of the non-cracked group.Because more micro-cracks are closed under loading,the peak rate of the total damage variable of the cracked SCC under uniaxial compression is lower than that of the non-cracked group,while the corresponding peak Strain increases significantly.Freeze-thaw cycles produce freeze-thaw denudation effects on the inner wall of cracks,resulting in a significant increase in the width and area of macroscopic cracks in SCC.(3)The variation of the SCC performance of the filling layer under various working conditions is analyzed by finite element calculation.The stiffness of the filling layer SCC under freezing and thawing is obviously degraded,which leads to the continuous increase of the actual stress level,among which the tensile stress level increases the most,and the structure is prone to tensile stress damage.The influence of different position loads on the performance of SCC is analyzed.The crack stress intensity factor at the end of the plate is larger,and it is easier to crack and expand.It needs to be paid attention to when the structure is repaired and maintained.86 figures,42 tables,86 references.