不同受力模式下的沥青混合料接触力链分布特征

Contact force chain distribution characteristics of asphalt mixture under different stress modes

摘要:

为了研究拉压弯剪不同受力模式下沥青混合料内部的接触力链传递分布情况,明确骨料砂浆不同组分抵抗荷载时的各自贡献水平,基于工业CT与数字图像处理技术获取了骨料颗粒模型,利用PFC3D软件构建了SMA13级配的沥青混合料三维数字化试件并进行了不同受力模式下的虚拟试验,对沥青混合料内部接触力链的传递分布特征以及砂浆骨料不同组分的接触力组成分布情况进行可视化及量化分析,以力链概率作为量化指标对不同受力模式下各类接触力链的分布特征进行统计分析。研究结果表明:利用离散元方法建立的三维数字化模型可以较好地模拟沥青混合料低温力学行为;单轴压缩受力模式下各类接触的强力链占比均为4种受力模式当中的最高水平,骨料间的嵌挤作用为抵抗外载的主要因素,骨料所传递的接触力水平占总接触力的69.9%；间接拉伸与半圆弯拉载荷模式下,沥青砂浆内部与界面位置的强力链占比显著高于骨料间的强力链占比,沥青砂浆所传递的接触力分别占总接触力的50.1%和57.4%,沥青砂浆间的黏结力为抵抗破坏的主导因素；单轴贯入受力模式下沥青砂浆与界面位置的强力链占比略高于骨料间接触的强力链占比,骨料所传递的接触力占总接触力的64.7%。强弱力链占比可以较好地反映沥青混合料不同组分在不同受力模式下的传递载荷能力,依据研究结果可以从细观结构角度为深入了解沥青混合料的力学行为提供理论依据。

Abstract:

In order to study the transmission and distribution of contact force chain in asphalt mixture under different stress modes of tension, compression, bending and shearing, clear different aggregate mortar components resistance load in the respective levels of contribution, based on industrial computed tomography (CT) and digital image processing method for aggregate particle model, using software PFC3D constructed SMA13 gradation of asphalt mixture of 3D digital specimen, and virtual tests were carried out under different stress modes. The transfer and distribution characteristics of contact force chain inside asphalt mixture and the distribution of contact force composition of different components of mortar aggregate were visualized and quantitatively analyzed. At the same time, the force chain probability was used as a quantitative index to analyze the distribution characteristics of various contact force chains under different force modes. The results show that the three-dimensional digital model established by discrete element method can better simulate the low temperature mechanical behavior of asphalt mixture. In uniaxial compression mode, the ratio of all kinds of contact strong chains is the highest among the four stress modes. The interlocking extrusion between aggregates is the main factor to resist external load, and the contact force level transmitted by aggregates accounts for 69.9% of the total contact force. Under indirect tensile and semi-circular flexural loading modes, the proportion of the strong chain between the interior and interface of asphalt mortar is significantly higher than that between aggregate. The contact force transmitted by asphalt mortar accounts for 50.1% and 57.4% of the total contact force, respectively. The bond between asphalt mortar is the dominant factor to resist damage. In uniaxial penetration force mode, the proportion of strong chain between asphalt mortar and interface is slightly higher than that between aggregate, and the contact force transmitted by aggregate accounts for 64.7% of the total contact force. The ratio of strong and weak force chain can better reflect the load transfer capacity of different components of asphalt mixture under different stress modes. The results can provide theoretical basis for understanding the mechanical behavior of asphalt mixture from the perspective of meso-structure.