| With the rapid development of China’s economy,high-speed and safety requirements are put forward for railway system.Ballastless track has been widely developed and applied because of its good smoothness and high stability.CRTS type Ⅱ plate-type ballastless track is one of the most widely used ballastless track types in China,accounting for about one-third of the total mileage of China’s high-speed railway ballastless track,and the total mileage of its double track has reached 4852km.In this paper,relying on the Youth Project of National Natural Science Foundation of China(51808056)"Fatigue Damage Mechanism of interface of concrete-cement emulsified asphalt Mortar under temperature Load and repeated action of train",the shear debonding damage(disjoint)of interlayer interface of CRTS Ⅱ plate-type ballastless track in practical engineering was studied.The shear bond properties were studied from two angles of experiment and finite element simulation:1.The single shear static tests of 12 concrete-CA mortar composite specimens were completed.The failure mode of interlayer interface was brittle failure,and the shear strength and shear load-relative(absolute)displacement curves of interlayer interface were obtained.The damage factor relative displacement curve of interlayer interface was obtained by using damage factor parameters,and the damage degree of interlayer interface during elastic-plastic deformation was analyzed quantitatively.From the perspective of energy,the evolution law of fracture energy of interlayer interface of composite specimen was given,and the whole process of interlayer interface from loading to damage to failure was analyzed quantitatively.2.A finite element model of single shear interface is established for static test of single shear interface.In the finite element model,the bilinear cohesive force model was used to describe the shear cracking behavior of the interlayer interface of concrete-CA mortar composite specimen.The evolution process of the stress and strain cloud map is consistent with the experimental phenomenon.The load-relative displacement curve,damage factor-relative displacement curve and fracture energy-relative displacement curve obtained by finite element analysis are in good agreement with the experimental results.Based on the proposed characteristic parameters of bilinear cohesive force model,a local shear stress-slip constitutive model of the interface between concrete and CA mortar layers was proposed.3.The 15 interlayer oblique shear finite element models with different inclined angles were established to investigate the load-relative displacement relationship of the interlayer between concrete and CA mortar under composite stress state.By regression analysis of the finite element model results,the relative formulas of tangential limit relative displacement,shear forward stiffness and shear pressure ratio were obtained.This formula can accurately describe the shear bond performance of the interlayer interface of concrete-CA mortar under the state of composite stress even when the interlayer inclination Angle is close to 0° and 90°.4.The single shear fatigue tests on interlayer interface of 15 concrete-C A mortar composite specimens under different stress levels were carried out,and the failure mode of interlayer interface was brittle failure.The relationship between the stress level of interlayer interface and fatigue life is discussed.Based on the linear regression analysis of single shear fatigue test results of composite specimens,the S-N relationship model was obtained,which can accurately describe the shear bond performance ofthe interlayer interface of concrete-Ca mortar composite specimens under repeated loads.The research work in this paper can provide reliable data and theoretical support for the shear debonding failure of interlayer interface of CRTS Ⅱ plate-type ballastless track in practical engineering,and has certain guiding significance for the safe service of interlayer interface. |
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