Research On The Expansion Law Of Reflection Cracks In Asphalt Pavement Based On Discrete Element Method

Asphalt pavement is one of the most common pavement structures in high-grade roads due to its good road performance and construction and workability.However,with the extension of service life,the reflective cracking disease of asphalt pavement occurs frequently,leading to a significant reduction in the performance and service life of the pavement.In order to investigate the influence of different factors on the propagation law of reflective cracks,this study uses the discrete element simulation method to quantitatively analyze the propagation potential of reflective cracks according to the mechanical response changes at the reflective crack,and explores the development trend of reflective cracks under different pavement structure combinations.This provides theoretical support for characterizing the evolution of reflective cracks in asphalt pavement and resisting crack initiation.Initially,uniaxial compression tests were conducted on asphalt mixtures,and a corresponding discrete element model was constructed.The material parameters of the asphalt mixtures were determined by comparing the results of laboratory experiments with those of discrete element simulations.In the construction of the discrete element model,the asphalt mixture was regarded as a three-phase composite material consisting of coarse aggregates,asphalt mortar,and voids.A discrete element asphalt pavement model was constructed using Ball elements.Furthermore,a finite element model was established with the same parameters and subjected to the same load as the discrete element model.The mechanical response results of the two simulation methods were compared to verify the accuracy of the discrete element model and the reliability of the obtained micro-material parameters.Next,a wheel-load model similar to the actual wheel load was established to apply rolling loads to asphalt pavement structures under different conditions such as layer thickness,cracking position,cracking width,load axle weight,and cracking depth.The mechanical response results at different crack locations were recorded and analyzed.The results showed that increasing the thickness of the asphalt layer can effectively reduce the potential for reflection crack propagation.Increasing the cracking position,cracking width,cracking depth,and load axle weight can accelerate the crack propagation trend and increase the potential risk of crack generation.Then,based on the grey correlation analysis method,the degree of correlation between different influencing factors and different mechanical response indicators is quantitatively analyzed.According to the comprehensive correlation results,with the influencing factors as the reference sequence,the vertical stress at the crack tip and the thickness of the surface layer,crack width,and axle load have the highest correlation degree.The lateral displacement on both sides of the crack has the highest correlation degree with the crack initiation location and depth.With mechanical response as the reference sequence,the thickness of the surface layer has the highest correlation degree with the transverse stress at the crack tip and the lateral particle displacement on both sides of the crack.The crack width has the highest correlation degree with the shear stress at the crack tip.The axle load has the highest correlation degree with the vertical stress and vertical displacement at the crack tip.Finally,by changing the combination of surface layer thickness,base layer thickness,and base layer modulus,different asphalt pavement models are constructed,and the same rolling load is applied to analyze the influencing factors and propagation laws of reflection cracks in different asphalt pavement combinations.The analysis results indicate that,while the total thickness of the asphalt surface layer remains unchanged,an increase in the thickness of the lower layer will reduce the stress level at the reflection crack and delay the expansion of the reflection crack.An increase in the thickness of the base layer can to some extent resist the expansion of reflective cracks in the surface layer,but the impact is relatively small.Increasing the modulus of semi rigid base can reduce the stress level at the crack site and reduce the potential for reflective crack development.Based on the above analysis results,it is determined that in the pavement structure with AC-13 asphalt mixture on the upper layer and AC-20 asphalt mixture on the lower layer,and a semi rigid base layer,the thickness of the upper layer is 3.5 cm,the thickness of the lower layer is 6.5 cm,the thickness of the base layer is 25 cm,and the modulus of the base layer is 1.4 times the standard modulus.The combination form of asphalt pavement is the most effective in resisting the expansion of reflection cracks...