采用离散元方法评价集料的骨架结构

为了从细观结构角度深入研究骨架型沥青混合料集料的受力特征,在离散元程序PFC3D内,采用多球相互重叠的方法描述粗集料颗粒的三维不规则形状,并建立了考虑级配特征的集料混合物生成方法.按照集料粒径由大到小的顺序,在PFC3D中对各档集料进行了虚拟的逐级填充,并定量分析了各粒径集料对逐级填充后混合物中集料间隙率、集料之间的接触点数量、接触力等参数的影响.结果表明:集料混合物中,较粗集料受到的接触力大于较细集料;在较粗集料的混合物中,加入大于2.36 mm的较细集料有助于增加集料混合物的接触点数量,降低较粗集料所承担的接触力;粒径4.75～9.50 mm集料对接触点数量的增加最为显著;4.75 mm是骨架型沥青混合料的关键粒径.

Evaluation of aggregate skeleton structure using the discrete element method

3D aggregate particles with irregular shapes were modeled using clumps of spheres within particle flow code in 3-dimensions(PFC3D) to investigate the mechanical characteristic of skeleton structure in asphalt mixture.The method to generate digital aggregate blends with given gradations were established in PFC3D.Particles sequential packing of different gradations was simulated using user-defined packing procedures.The air voids,the mean contact number of each size particle and the force proportion taken by aggregate particle of different sizes were investigated for the digital blends.Results show that the major part of load is transferred through the bigger aggregate particles rather than the smaller aggregates when load is applied on the blend sample.In blends containing coarser aggregate,the addition of finer aggregates that are larger than 2.36 mm is found beneficial in increasing the number of contacting points and therefore,reducing the contacting force undertaken by the coarser aggregates.It is observed that the addition of aggregates sized 4.75 to 9.50 mm can help increase the contacting points most efficiently,and the proportion of aggregate with size of 4.75 mm is crucial in the skeleton of asphalt mixture.