非均匀多孔沥青混合料中水流的三维细观渗透行为

Moisture is one of the most serious diseases for asphalt pavement in the world, the action effect of water flow in the internal of asphalt pavement is a key factor resulting in moisture. The permeation behavior has not been explained clearly using the conventional methods. This project will focus on the 3D microstructure of asphalt mixture with the X-ray CT（Computerized Tomography）and 3D digital test technology. The 3D distribution of voids will be characterized exactly and the connectivity of voids will be identified accurately, moreover, the 3D reconstruction algorithm will be optimized deeply and then the digital samples which reflect the real 3D structure of asphalt mixture will be reconstructed. In terms of the permeameter improved and combing the 3D fluid model, the dynamic permeation behavior simulation will be conducted under different hydraulic gradient directions （horizontal direction and vertical direction）and different hydraulic pressure patterns(steady pressure, pulsatile pressure and high pulsatile pressure). The velocity flow paths, water pressure transport, scouring effect and turbulent flows will be investigated respectively. Consequently, the numerical prediction method of directional hydraulic conductivity will be established, furthermore, the dynamic 3D visualization flow model will be constructed.This study can increase the microscale permeation mechanistic understanding of water flow in the internal asphalt mixture from a new angle of the view. This research will form the basis of theory and technology for controlling the moisture effectively.

沥青路面水损害是世界各国面临的重大难题，而水流在沥青路面内部的作用效应是导致其水损害的关键因素。以往研究方法尚未确切阐明水流在混合料内部的渗透行为，本项目拟从沥青混合料的三维细观尺度入手，借助X-ray CT（Computerized Tomography）和三维数值模拟技术，准确表征沥青混合料内部空隙的三维分布，精细识别空隙的连通特征，深度优化现有沥青混合料的三维重构算法，构建反映沥青混合料内部真实三维形貌的数值试样，结合改进的渗透测试装置以及三维流体模型，模拟在不同水力梯度方向和不同水压力模式（稳态、脉动和高脉动）下，水流在混合料细观空隙内的流速、流动路径、水压力传导、冲刷效应以及瑞流特征，并据此建立不同方向上渗透系数的数值预测方法，构建沥青混合料内部动态三维可视化流场模型。本项目旨在从新的视角揭示封闭混合料内部水流的细观渗透规律，为有效控制水损害奠定理论和技术基础。

水流在沥青混合料内部的渗透行为是沥青路面损害的关键因素，以往都是从宏观尺度研究沥青路面的水损害行为。我们针对水流在沥青路面内部的细观水损害行为开展深入研究。首先，借助X-ray CT（Computerized Tomography）和三维数值模拟技术，表征沥青混合料内部空隙的细观分布，识别混合料内部的空隙特征，针对材料密度连续变化特点，结合数字图像处理技术，对CT图像进行高斯平滑和H-maxima转换，以消除图像噪音和降低图像内颗粒像素密度变异性，重点研究分水岭分割算法在沥青混合料CT图像中的实现，对图像内粗集料进行分割与参数量测，并对所提出的方法进行级配验证，获得了一系列研究成果，这是对沥青混合料内部三组份（集料、砂胶和空隙）精细分割的基础；改进了渗透测试装置进行沥青路面渗透行为模拟，对稳态水压力模式的水流渗透冲刷行为取得一定成果。本项目的研究从细观视角揭示封闭混合料内部水流的细观渗透规律，为有效控制水损害奠定理论和技术基础。