弯剪组合作用下沥青混合料非线性疲劳损伤特性研究

In order to better simulate the internal complex stress state of asphalt pavement under the action of repeated loads, it is needed to study the fatigue characters of asphalt mixture under the combination effect of bending and shear force. Then the process of fatigue damage can be simulated more correctly..The change law between the strength and the loading rate can be obtained by the strength tests under different loading rate and different stress states. Then the real stress ratio of fatigue tests can be determined. The fatigue equation based on the real stress ratio can be established. It can be extended back to the strength failure point, where the fatigue life is 1. It also can reveal the internal relationship between the strength failure and the fatigue failure. In view of the above, a new method can be introduced to calculate the tensile strength structure coefficient..The axle load conversion method of the current specifications for design of highway asphalt pavement is established by the Miner linear fatigue damage theory. It can not consider the nonlinear effect which was caused by the change of the loading history. The load action is underestimated. It causes that a great deal of early damage is appeared of asphalt pavement. Based on the analysis of the strength and the modulus decay law during the process of the fatigue failure for asphalt mixture, the suitable damage variable can be raised. The nonlinear fatigue damage evolution equation can be established. The new axle load conversion method can be put forward. The new conversion method can consider the influence of the loading history and the damage evolution history simultaneously.. The research result will supply the theoretical basis for the calculation of the tensile strength structure coefficient and the axle load conversion.

为了更好地模拟重复荷载作用下沥青路面结构内部的复杂应力状态，需对弯剪组合作用下的沥青混合料疲劳性能进行研究，以期较真实反映其疲劳破坏过程。.通过不同加载速率和应力状态下的强度试验，得到沥青混合料强度随加载速率的变化规律，由此确定疲劳试验时的真实应力比，建立基于真实应力比的疲劳方程，该方程能后延到疲劳寿命为1的强度破坏点，能够揭示强度破坏和疲劳破坏的内在联系；据此,提出新的沥青路面抗拉强度结构系数计算方法。.规范基于Miner线性疲劳损伤理论建立的轴载换算方法无法考虑加载历史变化引起的非线性效应，低估了荷载的作用，造成沥青路面结构出现大量早期破坏。通过对沥青混合料疲劳破坏过程中强度与模量衰变规律的分析，提出合适的损伤变量，建立其非线性疲劳损伤演化方程，提出可同时考虑加载历史与损伤演化历史影响的沥青路面轴载换算新方法。.研究成果将为沥青路面抗拉强度结构系数计算和轴载换算提供理论依据。

我国沥青路面使用寿命往往难以达到设计年限，除材料、施工和超载等因素外，现有疲劳设计体系所存在的诸多问题亦为其主要原因。项目研究解决了复杂应力状态下沥青混合料非线性疲劳损伤特性的相关问题。. 通过系统的理论分析与室内外试验，发现沥青路面在轮载作用下处于三维应力状态，我国现规范以一维应力状态下的最大拉应力强度理论作为破坏准则，不能真实反映结构的抗力，故研发了一种复杂应力状态下强度试验新方法-气囊三轴试验，建立了三维复杂应力状态下沥青混合料的破坏准则，揭示了沥青混合料强度随加载速率变化的规律；建立了基于真实应力比的沥青混合料疲劳方程，并创建了基于真实应力比疲劳方程的沥青路面抗拉强度结构系数计算新方法，弥补了现设计规范在设计标准确定方面的不足。. 在对沥青路面材料疲劳试验结果分析的基础上，建立了动模量和剩余强度的幂函数衰变模型，揭示了重复荷载下沥青混合料刚度和强度的非线性衰变规律，构建了基于刚度衰变和剩余强度的非线性疲劳损伤演化方程；突破经典Miner线性损伤准则的局限性，提出了能同时考虑加载历史与损伤演化历史影响的沥青路面轴载换算新方法，为沥青路面荷载作用效应分析的科学性提供了重要依据。. 项目研究完成了计划书规定的研究内容，实现了预期研究目标，达到了预期研究目的。研究成果授权发明专利1项，发表学术论文8篇，其中SCI收录2篇，EI收录3篇，培养博士生1名，硕士研究生7名，举办或参加国内外学术会议4次。