两种不同模式下的沥青混合料断裂过程研究

A Numerical Analysis of the Fracture Behavior of Asphalt Concrete under Two Different Modes

为了深入研究沥青混合料在Ⅰ型和Ⅰ-Ⅱ复合型模式下的断裂特性与机理，采用了扩展有限元方法对单边切口梁的断裂过程进行了数值模拟和分析．通过与试验数据的对比发现，扩展有限元方法可以有效地计算不同模式下裂缝扩展的路径以及断裂过程中的力学响应．进一步分析表明：小梁的断裂过程可以分为4个阶段；当加载点的荷载达到峰值时，小梁已经处于损伤累积阶段，荷载开始下降后，裂缝才逐渐形成；断裂过程可以理解为损伤带内拉应力下降、未损伤带内拉应力上升或者上升后再下降的过程，且损伤带长度不断增加；Ⅰ-Ⅱ复合型断裂的临界偏移系数为0．45～0．51，与试验结果基本一致；当偏移系数为0．45时，跨中局部区域在加载过程中出现了“卸载”现象，导致损伤不再增加，抑制了次裂纹的产生．

In order to study the fracture behavior of asphalt concrete under pure modeIand rnixecl-moaeⅠ-Ⅱ, an Extended Finite Element Method （XFEM） was employed to simulate the fracture process of single-edge notched beam specimen （SEB）. Based on the comparison of numerical results and experimental records, it can be concluded that XFEM can serve as an efficient tool for the simulation of crack path and calculating mechanical response. Moreover, the fracture of SEB can be divided into four stages. The beam has already been under damage accumulation stage when the load reaches the peak value and crack initiates after the peak load. Fracture behavior can be considered as a process in which tensile stress decreases in the damaged zone and increases in the undamaged zone. Meanwhile, the length of the damaged zone is increasing. The critical offset coefficient obtained through numerical analysis is 0. 45 - 0. 51, which shows good agreement with the test result. Unloading behavior occurs near the mid-span section when offset coefficient is equal to 0.45, which inhibits the damage growth and the initiation of secondary cracks.