Study On Mesomechanics Of Non-homogeneous Cement Stabilized Macadam Based On Particle Flow Theory

Cement stabilized macadam is an important constituent material for high-grade pavement subbase structures,and its structural stability directly impacts the road’s service life and level of service.Therefore,it is necessary to explore its damage mechanisms in depth in order to enhance its structural stability and durability.Cement stabilized macadam,as a multiphase material composed of aggregates,mortar,and interfacial transition zone,is analyzed from a microscopic and nonhomogeneous perspective using the discrete element theory to investigate mechanical damage and microscopic mechanical behavior.Firstly,based on the damage constitutive relationship of cement stabilized macadam,a coupled damage constitutive model considering load and water immersion is proposed,and the nonlinear process of early-stage air compression is distinguished from the later linear loading process for theoretical optimization.Laboratory immersion damage tests are conducted to validate the feasibility of the theoretical model.A discrete element model is created to simulate the loading process of weakened specimens due to water immersion,allowing for a comparison of macroscopic and microscopic mechanical behaviors.The study reveals that the distribution of tangential contact forces is greatly influenced by direction,with significantly lower contact forces observed in the horizontal direction(around 0° and 180°)and vertical direction(around90° and 270°).Unlike the initial uniform distribution in all directions,the normal contact force in the peak stage rapidly increases in the vertical direction(around 90°).When the homogeneity factor is small,the model strength increases rapidly.However,after reaching the critical value of 20,the influence diminishes rapidly,with only minor fluctuations observed.Secondly,a uniaxial compression discrete element model of cement stabilized macadam is created,incorporating pre-existing cracks to simulate the response of the microstructure to different widths and densities of initial defects.The model investigates the development of the microstructure during the loading process,the distribution of crack quantities/angles at different stages,the state of normal/tangential force distribution,and the variation of model coordination number.Furthermore,a three-dimensional fatigue damage model is developed,incorporating multiple contact models to apply cyclic loads.The model incorporates a nonhomogeneous distribution function for microstructural parameters and is compared with a homogeneous model without the distribution function.The model monitors the microstructural damage,force chain and contact force states,microcrack quantities and distributions,while considering the intrinsic connection between multiple energy fluctuations during the damage stages.The analysis reveals that the homogeneous frictional energy growth rate of 66.30 is significantly higher than the nonhomogeneous growth rate of 9.46.Both models show similar trends in damping energy and impact energy changes,but the nonhomogeneous model has lower values.The bond energy and strain energy exhibit periodic fluctuations during the mid-loading phase and have similar fluctuation ranges.Finally,a three-dimensional crushed stone geometry is created through image recognition,and high-precision particle clusters are generated in the discrete element software as templates for generating optimized models.Gaussian,logarithmic-normal,and Weibull distribution models are assigned to the internal parameter distributions of the model,and the accuracy of the model is validated using experimental results.The stress peak error and elastic modulus error are both less than 2%.The analysis compares the distributions of the model radius multiplier,crack propagation trends,normal and tangential stresses,and contact bond damage rate under different distribution states.