移动荷载下含纵横向双裂纹沥青路面复合断裂特性

为了研究移动荷载作用下沥青路面的复合开裂的变化规律，基于断裂力学及有限元数值模拟方法，考虑沥青面层材料的粘弹性，分别研究了移动荷载作用下不同双裂纹间距、不同反射裂纹深度对面层top-down（纵向）、基层反射（横向）裂纹应力强度因子的影响，探讨了其开裂扩展特性，评估了不同移动荷载状态下面层top-down裂纹的断裂疲劳寿命.结果表明:移动荷载作用下，面层top-down裂纹以Ⅱ型扩展为主，在单裂纹及双裂纹间距为0时，分别对应其扩展最严重与最轻微情形，但双裂纹间距及反射裂纹深度对其扩展影响较小；对于基层反射裂纹，当双裂纹间距为400 mm时，最易发生Ⅰ、Ⅱ型开裂扩展，随着反射裂纹深度的增加，扩展程度也逐渐增大；不同移动荷载状态下的top-down复合型裂纹断裂疲劳寿命长短顺序为:高速最长，次之静态、低速制动最短，制动情形下的疲劳寿命仅为高速情形下的20.4%. 

Characterization of Vertical and Horizontal Propagations of Double Cracks in Asphalt Pavements under Moving Loads

The purpose of this research is to analyse the evolution of vertical and horizontal propagations of double cracks in asphalt pavements under moving loads using fracture mechanics and finite-element numerical simulations. In this regard, the effects of cracking space and reflective cracking depth on surface top-down cracking and base layer reflective cracking were studied by considering the viscoelastic behaviour of the surface material. Subsequently, crack propagation was characterized and the fatigue lives due to surface top-down cracking under different moving load levels were evaluated. The results indicated that surface top-down cracking mainly occurred in the type Ⅱ mode. Moreover, the cases of single crack and zero crack spacing corresponded to the conditions of most critical and noncritical propagations, respectively. However, crack spacing and the depth of reflective cracking did not have a significant influence on its propagation. For base layer reflective cracking, the most severe type Ⅰ and Ⅱ propagations occurred within a 400 mm cracking space, and the crack propagation level grew with increasing depth. The fatigue lives due to top-down mixed mode cracking under different moving load levels ranked in descending order as high speed, static state, low speed, and braking state. The fatigue life in the braking state was only 20.4% of that in the high-speed state.