沥青混合料动态模量预估模型研究进展

由于沥青路面结构受到车辆荷载、环境等因素的不断变化作用,它的实际工作状态与静态体系在材料性质等方面存在较大差距。因此,针对动态荷载作用下沥青路面结构的动态参数和动力特性的研究十分必要。沥青混合料动态模量是沥青路面设计的重要参数之一,通过室内试验测得沥青混合料不同温度、频率下的动态模量,然后绘制主曲线,可准确预测不同温度、频率及极端条件下沥青混合料的动态模量。然而,目前沥青混合料模量测试方法复杂、试验成本较高,因此寻求简便的方法获得或预估沥青混合料的模量成为近年来研究的热点。为此,已有众多学者针对沥青混合料动态模量预估模型进行了研究。典型的预估模型包括Witczak 1-37A模型、NCHRP 1-40D模型和Hirsch模型等,尽管这些模型是在大量试验数据的基础上拟合得到,但由于世界不同地区的材料、试验方法、环境条件等存在差异,致使三种经验预估模型在不同地区的适用性也不尽相同。与此同时,随着计算机技术的发展,研究人员逐渐从微观角度建立模型来预测混合料的动态模量,而在沥青混合料数值模拟方面,离散元法(DEM)具有其他数值模拟方法无可比拟的优势。在典型预估模型的适用性方面,国外针对沥青混合料动态模量的预估做了大量研究,对几种典型的动态模量预估模型的适用性进行了系统分析,并提出了具体的修正模型。但目前我国在预估模型方面的研究只集中于个别省份和地区,而全国范围内沥青混合料动态模量的综合测试较少,缺乏有效的预估模型基础数据,因此针对我国不同地区沥青混合料动态模量的预估模型有待进一步深入研究。在沥青混合料细观模型方面,基于CT图像处理技术的离散元仿真试验,可建立以真实试件为依据的虚拟几何模型,其中集料形状、分布以及空隙特征都可与实际情况一致,从而进行良好的虚拟仿真试验。本文归纳了沥青混合料动态模量预估模型的研究进展,分别对沥青混合料动态模量预估模型以及各预估模型在不同地区的适应性进行了分析,并介绍了基于DEM的动态模量预测方法。最后,分析了沥青混合料动态模量预估模型研究面临的问题并展望了其应用前景,以期为沥青混合料动态模量预估模型在我国沥青路面设计中的研究和应用提供参考。

A Review of Dynamic Modulus Prediction Model of Asphalt Mixture

Owing to the variation of vehicle load and environmental conditions, there exist huge difference between the actual working state and the static state in the material properties of asphalt pavement. Hence, it is necessary to investigate the dynamic characteristics of the asphalt pavement under dynamic load. The dynamic modulus of asphalt mixture is one of the important input parameters in asphalt pavement design. Usually, the master curve of asphalt mixture, fitted by the dynamic modulus of different temperatures and frequencies, can be used to accurately predict the dynamic modulus of asphalt mixture under different temperature, frequency and extreme conditions. Nevertheless, the complexity and high cost of indoor tests have hindered the application of modulus test of asphalt mixture. Therefore, exploring a more convenient way to obtain or predicate the dynamic modulus of asphalt mixture has become a research hot spot in recent years. There has been numerous studies on dynamic modulus prediction model. Several classical models like Witczak 1-37A, NCHRP 1-40D and Hirsch have been proposed. Although the three models are fitted on the basis of a large number of experimental data, the applicability of them are different because of the differences of materials, test methods and environment conditions in various regions of the world. Besides, with the development of computer technology, researchers endeavor to build simulation models in microscopic view to predicate the dynamic modulus of asphalt mixture in recent years. Specially, discrete element method (DEM) shows great advantages and has been widely used to simulate the asphalt mixture materials. In terms of applicability of the typical prediction models, a large number of studies on dynamic modulus prediction of asphalt mixture have been carried out by foreign scholars. The applicability of the three typical prediction models are systematically analyzed, and specific revision models have been put forward. However, the researches of the prediction model only restrict to few provinces and regions in China. It lacks nationwide comprehensive research on the dynamic modulus of asphalt mixture, which leads to the insufficient data base for revising the prediction model. All in all, there is an urgent need for further investigating the dynamic modulus prediction of asphalt mixture in different regions of China. For the microscopic simulation model of asphalt mixture, the DEM with CT technology can create a virtual specimen model, in which the aggregate shape, distribution and void features are in consistent with the actual situation, and the simulation test can be carried out accurately. This article summarizes the status quo of dynamic modulus prediction model of asphalt mixture. The three classical dynamic modulus prediction model and their applicability in different regions are introduced and analyzed. Besides, the discrete element me-thod (DEM) that used to predict the dynamic modulus of asphalt mixture is elaborated with emphases. At last, the current drawbacks existing in this technology are pointed out and the future research trends are proposed, which expected to provide a reference for the research and application of the dynamic modulus prediction model of asphalt mixture.