动载下复合式基层沥青路面的裂缝扩展行为研究

Study on Crack Propagation Behavior of Composite Base AsphaltPavement Under Dynamic Load

基于断裂力学理论及有限元数值模拟方法,建立塞内加尔MBOUR-KAOLACK(MK)高速公路带裂缝的复合式基层沥青路面三维模型,分析了不同荷载与路面结构层参数对复合式基层沥青路面开裂初期应力强度因子的影响,并与等厚半刚性基层路面对比,分析了裂缝在向上扩展时应力强度因子的变化规律。结果表明:随着车速的降低或轴重的增大,应力强度因子极值逐渐增大,路面裂缝扩展的风险增大。随着路面结构层厚度和沥青层模量的增大,应力强度因子则均在减小。其中,增大半刚性底基层与增大面层厚度对应力强度因子的降幅相近,故增大半刚性底基层厚度更经济。不过,底基层模量的增大会导致应力强度因子增大,也应避免使用过高模量的底基层。随着裂缝向上扩展,复合式基层沥青路面和半刚性路面的KⅠ先增大后减小,KⅡ逐渐增大,开裂主导模式逐渐由张拉型转变为剪切型。在裂缝向上扩展的过程中,复合式基层沥青路面的KⅠ降幅比半刚性基层路面更大,且其应力强度因子也小于半刚性基层沥青路面。可见,复合式基层沥青路面的抗裂性更好。

Based on the theory of fracture mechanics and finite element numerical simulation method,a three-dimensional model of the composite base asphalt pavement with a crack on Senegal MBOUR-KAOLACK(MK)expressway was established.The influence of the load and pavement structure layer parameters on the stress intensity factor of the composite base asphalt pavement at the initial stage of crack propagation was analyzed.The variation law of stress intensity factor when the crack expands upward was analyzed,and compared with the semi-rigid base pavement with equal thickness.The results showed that the extreme value of the stress intensity factor increased gradually with the decrease of vehicle speed or the increase of axle load,leading to the risk of pavement crack propagation increases.The higher the pavement structure layer thickness and asphalt layer modulus,the lower the stress intensity factor.Among them,increasing the thickness of the semi-rigid subbase and increasing the thickness of the surface layer had similar reductions in the stress intensity factor,so increasing the thickness of the semi-rigid subbase was more economical.However,the increase of the modulus of the subbase would lead to the increase of the stress intensity factor,and the use of a high modulus subbase should also be avoided.As the cracks expand upward,the KⅠof the composite base asphalt pavement and the semi-rigid pavement first increased and then decreased.The KⅡgradually increased,and the dominant mode of cracking gradually changed from the tensile mode to the shear mode.In the process of crack propagation upward,the KⅠdecline range of the composite base asphalt pavement was greater than that of the semi-rigid base pavement,and its stress intensity factor was also smaller than that of semi-rigid base asphalt pavement.It could be seen that the crack resistance of the composite base asphalt pavement was better.