Research On Construction Method And Mechanical Properties Of Mesoscopic Model Of Asphalt Mixture

It cannot accurately for the traditional macroscopic test method to describe the internal microstructure characteristics and mechanical properties changes of asphalt mixtures from a mesoscopic perspective.With the development and application of digital image processing technology and numerical simulation methods,a relatively complete digital image processing flow and meso-structure evaluation method for mixtures have been formed at home and abroad.This paper is based on CCD digital image technology and 3D laser scanning technology to obtain aggregate characteristics,combined with finite element method and numerical simulation method to conduct a virtual splitting test,and explores the impact of the microscopic characteristics of asphalt mixture on the macro-mechanical properties from a microscopic point of view..The main research content and research results are as follows:First,the CCD high-definition camera was used to complete the extraction of the aggregate image in the two-dimensional model of the asphalt mixture,and the 3D laser scanner was used to obtain the aggregate point cloud data of different origins.after that the database of 1050 two-dimensional aggregate particles and 528 three-dimensional aggregate particles were constructed respectively.The programming algorithms of aggregate extraction and aggregate morphological index evaluation have been completed to analyze the statistical distribution law of them,thus establishing the connection between the two-dimensional and three-dimensional characteristics evaluation indexes of aggregates.Then,according to the geometric distribution characteristics of 3D aggregates,developed an algorithm for generating 3D irregular virtual aggregates with controllable shapes and constructed a three-dimensional virtual aggregate library.Combined with numerical simulation methods,aggregates were randomly selected from the aggregate library,Adopting bounding box and spatial triangle pair method for aggregate interference detection,and constructing a three-dimensional numerical model of asphalt mixture.On this basis,the algorithm for cutting the cross-section of asphalt mixture 3D specimens was further developed and compiled to facilitate the 3D interior meso-structure.of asphalt mixture.Finally,the above-mentioned two-dimensional slice images were imported into finite element software,and a mesoscopic model of asphalt mixture containing aggregates and asphalt mortar(voids are regarded as part of the mortar)was constructed,and the generalized Maxwell bilinear model and cohesive zone model were used to carry out the finite element model of virtual indirect tensile test,to verifies the accuracy and rationality of the finite element method by comparing the load peaks in the indoor test and the simulation test.On this basis,the influence of factors such as different loading ways,gradation types,aggregate shapes and angular characteristics on the anti-cracking performance of asphalt mixtures is further analyzed.The research shows that: at the same temperature,when the loading angle is 135°,the anti-cracking effect of asphalt mixtrue is better;under certain temperature conditions,RT and ST show a good regularity with the angular angle,and when the FI is around 3.0,the maximum ST and the minimum RT can be found;There is a good relationship between the mechanical indicators and the gradation type.With the increase of the maximum nominal particle size of the aggregate,ST and RT show an increase or decrease trend respectively.