基于离散元法的多孔沥青混合料空隙衰变研究

Research on Void Reduction of Porous Asphalt Mixture Based on Discrete Element Method

为了研究加载后多孔沥青混合料的空隙衰变规律,使用离散元软件PFC2D生成了多孔沥青混合料的二维车辙板虚拟试件并模拟了车辙试验.在虚拟试件生成过程中采用了新的空隙生成算法,即按照空隙级配来模拟不规则多边形,将其投放在沥青砂浆内并删除后形成空隙.通过室内静态蠕变试验获取多孔沥青混合料的微观参数值,以此来设计虚拟车辙试验的加载方式、空隙信息提取算法,并将虚拟车辙试验结果与室内车辙试验结果进行对比,验证了虚拟车辙试验的可行性.虚拟试验结果表明:荷载越大,试件空隙衰变越明显;随着荷载作用时间的增长,试件空隙率持续衰减,但速率变缓,在混合料结构破坏之前存在趋于稳定的状态;环境温度对试件空隙率影响明显,随环境温度升高,空隙率的衰减呈现3阶段变化;试件初始空隙率为20%(体积分数)时,加载后其空隙率衰变值最小.

In order to analyze the void reduction of porous asphalt mixture after loading,the discrete element software PFC2 D was used to establish the two-dimensional digital specimen of porous asphalt mixture and virtual rutting test.New void generation procedure was developed,void graded in asphalt mortar was simulated as irregular polygons which were put into asphlt mortar and then deleted so that void was formed.The microscopic parameters of porous asphalt mixture were obtained by the static creep test.Loading modes and gap information extraction algorithm of the virtual rutting test were designed.The feasibility of virtual rutting test was verified by the comparison with lab rutting test.Through series of virtual tests under different factors,it is showed that void reduction increases as the loading increases;the rate of reduction slows down gradually to a stable state before the structure damage;temperature has great effects on the void reduction,and as the temperature increases,three stages of change is shown;the void reduction reaches bottom when the initial void ratio（by volume）is 20%.