STUDY OF CRACKING MECHANISM OF PRE-SPLITTING CRACK OF CRTS Ⅱslab TRACK UNDER TEMPERATURE GRADIENT

摘要

In order to study the cracking mechanism of pre-splitting crack of CRTS Ⅱ slab track under temperature gradient,the finite element method is adopted to establish a solid model of track structure and the impact of the temperature gradient to the mechanical characteristic of the pre-splitting crack and the whole track structure is analyzed.The results show that under the temperature gradient there is stress concentration at the pre-splitting cracks.Under positive temperature gradient,there is mainly compressive stress in the concrete which will not lead to cracking.However,under smaller negative temperature gradient of-30°C/m,the tensile stress at the pre-splitting crack is 6.1 MPa which exceeds the tensile strength of concrete.And this tensile stress inevitably leads to cracking in slab.When the cracks grow to transfixion cracks,the tensile stress of CA mortar sharply rises and exceeds the tensile strength.And this will lead to cracking in CA mortar.When there is only one transfixion crack in both slab and CA mortar,the maximum longitudinal tensile stress of supporting layer exceeds the tensile strength,and this will lead to cracking in the supporting layer.However,while the number of the transfixion cracks increases,the maximum longitudinal tensile stress of supporting layer decreases.So a transfixion crack may not form in the supporting layer.The cracking mechanism of pre-splitting crack plays an important role in the stability of the track structure.Cracks should be avoided,especially the transfixion cracks.