Discrete Element Simulation Of Asphalt Mixture Based On Aggregate Particle Breakage

There are many factors that affect the performance of asphalt mixtures.It is very difficult to analyze the influence of these factors and their interactions using traditional test methods,and it is difficult to analyze the internal composition structure and mechanical properties of asphalt mixtures at a meso level..In recent years,numerical simulation technology has been gradually applied to the material design and performance simulation evaluation of asphalt mixtures,and has become an effective tool for studying asphalt mixtures.However,most of the aggregate particle models used in numerical simulations are generated by CT scanning image processing technology and computer algorithms.,The aggregate particle model does not match the actual aggregate shape;more importantly,the aggregate particle discrete element model mostly uses multiple overlapping spheres to describe the geometric shape of the aggregate particles.The model has infinite stiffness and the volume cannot be changed.It also means that the discrete element model of aggregate particles is not allowed to break or break,which leads to the obvious inconsistency between the simulation results and the actual situation.Based on this,this paper uses three-dimensional structured light scanning technology to scan aggregate particles to build a breakable aggregate particle discrete element model.On this basis,this paper uses three-dimensional structured light scanning technology to scan the aggregate particles,and attempts to establish a discrete element model of the breakable aggregate particles based on the true aggregate particle morphology,the internal mechanical analysis model of the particles,and the simulation evaluation method of the mixture performance.The main contents are as follows :Firstly,in order to efficiently and accurately obtain the aggregate particle contour model based on the actual aggregate particle morphology,the three-dimensional structured light scanning technology is used to scan the real aggregate particles.This technology is a surface scanning technology,which can simultaneously scan one surface of the aggregate particles to be measured,accurately measure the complex curved contour information on the surface of the aggregate particles,and stitch each measurement surface to obtain the aggregate particle outline model.Compared with CT scan image processing technology and computer algorithm random generation technology,three-dimensional structured light scanning technology can quickly and accurately build aggregate particle contour models based on real aggregate particle morphology.Selecting coarse aggregates with typical shape characteristics,scanning these aggregates with structured light,and establishing an aggregate particle profile model database based on real aggregate morphological characteristics.Then,the crushing test of the aggregate mixture was carried out to study the form of aggregate particle damage,and it was found that the damage was mainly based on the crushing of the aggregate corners,and a small amount of aggregate particle fracture occurred as a discrete element model of aggregate particles The broken principle.According to the concentrated stress transmission path of the aggregate particles in the mesostructure of the asphalt mixture and its stress situation,four possible modes of aggregate particle damage are proposed: compression,crushing and compression,and shearing.Secondly,in order to obtain the discrete element model of damageable particles,a threedimensional model of aggregate particles filled with unequal radius sphere filling method is proposed.All filled spheres do not overlap each other,and the adjacent spheres are cut externally.A larger radius filled sphere is used to fill the internal space of the aggregate particle model.A small radius filled sphere ensures the corners and surface contours of the model.The benefits of unequal radius sphere filling are Not only can the damage mode of the model be consistent with the real aggregate mechanical state,but also the total number of spheres will not be too much,which affects the calculation efficiency of the model.Taking 95% volume filling degree as the filling effect evaluation index,it can be better Balance model accuracy and computational efficiency.The parallel bonding model is used to “bond” these spheres into a whole,thereby constructing a discrete element simulation analysis model of breakable aggregate particles.Thirdly,in order to more accurately simulate the actual fracture effect of the contact mechanical model between the filled spheres inside the particles,the contact parameters of the linear and parallel bonding model inside the discrete element model of the aggregate particles were calibrated.The parameters of the bonding model were modified to eliminate the difference in bond bond stress caused by the difference in the radius of the filled sphere.The crushing test of the discrete particle model of a single aggregate particle was used to verify the breakage characteristics of the discrete particle model of the aggregate particle.It is basically consistent with the crushing test results of real aggregate particles.Finally,in order to verify the impact of the particle damage situation on the performance of the asphalt mixture,a combination of indoor rotary compaction test,unconfined compression test and discrete element simulation was used to verify the discrete element of the breakable aggregate particles.Reliability and accuracy of model and virtual samples of asphalt mixture.Based on the rotation compaction test,uniaxial compression test and its volume and mechanical indexes,the discrete element model of breakable aggregate particles is closer to the indoor test results.The results show that compared with AC and SMA grades,OGFC has the smallest internal force growth rate with the increase of compaction displacement.The 15% content of needle-shaped particles obviously hinders the transfer of internal stress of the mixture and may cause more aggregates.The particles are broken,and the increase of needle-like particles under indoor conditions makes the asphalt mixture difficult to compact.