Fatigue Properties And Ice-breaking Mechanism Study Of Crumb Rubber Modified Asphalt Mixture On DEM

At present，the study field of the asphalt mixture mainly focused on exploring theoccurrence mechanism from its macroscopic perspective. In fact， the essence of macroscopicphenomena needs from microcosmic mechanism， which is the key point of all kinds ofcomplicated asphalt pavement engineering problems for their researchs.Studying from themicroscopic perspective is also the development trend for asphalt pavement engineeringresearches. The discrete element method is founded and developed by Cundall and Strack，whose important characteristic is discreteness.It can provide very good numerical analysistools， and also can give all kinds of information from microcosmic changes to themacroscopic response comprehensively.In addition to this，it can be used to discusseeffectively through the influence from all sorts of microcosmic parameters on themacroscopic phenomena further， which is conducive to revealing the macroscopicphenomenon of asphalt mixture essentially.Crumb rubber modified asphalt mixture is composed of coarse and fine aggregate whichare wrapped by the asphalt mortar materials and the particles of the crumb rubber unit,so it isa multiphase composite material, its engineering properties are quite complex. When theasphalt pavement is under traffic load, the single aggregate particles and a single crumbrubber both have a unique way of running, and they show a non-uniform and discretemechanical characteristics.This paper starts with the microstructure of the crumb rubber modified asphalt mixture,and it makes mix of discrete element analysis as the main line,from numerical simulationanalysis for three kinds of typical graded structure to the study on fractal graded of skeletondense structure. And then discusses the indirect tension test numerical model of mixture,establishes the corresponding relations of dissipated energy, fractal dimension with the fatiguelife of crumb rubber modified asphalt mixture. Through the analysis of the influence onice-breaking performances from rubber particle volume fraction, ice thickness andtemperature, proving the research conclusion of mixture ice numerical model, Thus it revealsthe ice-breaking mechanism of crumb rubber modified asphalt mixtures.Ultimately,theresearch results of fractal gradation and fatigue performance as well as ice-breakingmechanism were used in the grading components design of crumb rubber modified asphaltmixture. Through the entity engineering,verifying the microcosmic numerical simulation andindoor test research results, which provides certain theoretical guidance for the antifreezing asphalt pavement.This paper established microcosmic numerical model for three typical structure throughtheoretical analysis, and put forward microcosmic parameters mainly including the averageunbalanced force and average contact force and at the same time determined two macroscopicparameters which were the compressive strength and compressive modulus of resiliencethrough mechanical test. Comparative microcosmic numerical simulation and the conclusionobtained from mechanical test, it proved that the skeleton dense type structure is the mostsuitable for crumb rubber modified asphalt mixture from the macroscopic and microcosmictwo angles.In this paper,the splitting microcosmic numerical model of crumb rubber modifiedasphalt mixture made fracture number and indirect tension as the main microcosmicparameters,which was mutual verification with two macroscopic parameters called splittingtensile strength and stiffness modulus which were determined splitting test. It verified theadding of rubber particles would decrease the mechanical strength of asphalt mixture fromthe macroscopic and mesoscopic two angles.The paper constructed microcosmic numerical model which could reflect the interactionof different mixture and different ice thickness,the strain energy and particle displacement ofthe microcosmic parameters were compared with two macroscopic parameters named therally amount weighted average of BPN and the rally rate weighted average of BPN, whichrevealed the ice-breaking of the crumb rubber modified asphalt mixture from themacroscopic and mesoscopic two angles.In a word, discrete element method provides very good numerical analysis tools for themicrocosmic study of the crumb rubber modified asphalt mixture which makes discrete asimportant characteristics,which truly could explain the the essence of macroscopicphenomena from microcosmic mechanism, and it provides a new idea which makes testcombine with theoretical analysis to reveal early failure causes and explore the ice-breakingmechanism of crumb rubber modified asphalt mixture.