基于权函数法的沥青路面基-面层裂缝的扩展行为

Crack propagation behavior between base and surface courses of asphalt pavement based on weight function method

为了研究半刚性基层沥青混凝土路面在行车荷载作用下出现的基层反射裂缝及其扩展规律,基于黏弹性断裂力学理论和权函数法,对反射裂缝的应力强度因子进行了分析,推导了Ⅰ-Ⅱ复合型裂纹断裂判据理论.采用数值模拟方法分析了结构层厚度及荷载位置对基层反射裂缝的影响,并通过单边切口小梁试验研究了面层裂缝扩展模式.研究结果表明:Ⅰ型(K_Ⅰ)和Ⅱ型(K_Ⅱ)应力强度因子受路面结构层厚度的影响较大,在行车荷载作用下Ⅰ型裂纹扩展模式起主导作用,增加基层厚度对防止反射裂纹的产生有一定的效果;在考虑水平荷载作用时,Ⅰ型和Ⅱ型应力强度因子均随荷载位置的变化而变化,随着荷载与裂纹距离的不断增加,K_Ⅰ逐渐减小,K_Ⅱ逐渐增加,反射裂缝逐渐偏向Ⅱ型裂纹扩展模式;在不考虑水平作用时,基层反射裂纹以Ⅰ-Ⅱ复合型形式出现,并在应力集中下向面层扩展,扩展模式表现为Ⅰ-Ⅱ复合型.

In order to study the reflection cracks and the crack propagation regularity of semi-rigid base asphalt pavement under traffic load, the stress intensity factor of the reflection crack is ana- lyzed and the fracture criterion of Ⅰ-Ⅱ mixed mode crack is established based on the theory of viscoelastic fracture mechanics, using the weight function method. The influence that the structural layer thicknesses and the load position have on the reflection cracks within the base layer is analyzed by numerical simulation. The crack propagation pattern within the surface layer is studied through single-edged notched beam test. The results show that the stress intensity factor of type Ⅰ （K Ⅰ ） and that of type Ⅱ （K Ⅱ ） are both greatly influenced by the structure thicknesses of pavement, and the typeⅠ crack propagation pattern plays a leading role when the road is under traffic load.It is also found that increasing the thickness of base layer has some effect on preventing re flection cracks. When the horizontal load is taken into account, K Ⅰand K Ⅱ all change with the change of load position, and with the increase of the distance between the load and crack, KⅠ gradually decreases, while K Ⅱ gradually increases, so the reflection crack gradually turn to type Ⅱ crack propagation pattern. When the horizontal action is overlooked, the reflection cracks with- in the base layer appear in the form of Ⅰ-Ⅱ mixed pattern and extend to the surface layer under stress concentration, the extension mode of which is also shown as Ⅰ-Ⅱ mixed pattern.