考虑拉压模量不同的沥青混合料双模量本构模型与疲劳特性研究

Most pavement materials are non-uniform mixtures formed by roller compaction, whose tensile and compressive moduli are significantly different. However, the classical linear elastic theory based on the same modulus in tension and compression is still used in current pavement design method in China, resulting in a large deviation between the design results and the actual stress state of pavement. Therefore, typical pavement material-asphalt mixture is selected to establish its bi-modulus constitutive equation and fatigue damage equation taking into account the difference between tensile and compressive modulus in this project. By the mechanical tests of asphalt mixture in laboratory, its nonlinear mechanical properties between stress and strain and the nonlinear laws of elastic parameters are revealed. The bi-modulus constitutive model of asphalt mixture is constructed based on the test results of stress and strain and the basic mechanics principle (that is, the constitutive matrix is required to be symmetric and can revert to linear elastic constitutive when the tensile and compressive modulus are equal). Based on the bi-modulus theory, the bending fatigue tests of beam under full sine wave loads are carried out to reveal the fatigue decay law on the modulus of asphalt mixture and establish the fatigue damage equation on the basis of stiffness decay. Hereby the method which characterizes fatigue properties of asphalt mixture based on bi-modulus theory is established. The research results can provide a basis for establishing the mechanical calculation and anti-fatigue design method considering the different mechanical properties of pavement materials in tension and compression and the force characteristics of pavement structure under the alternate load of tension and compression.

绝大部分路面材料为碾压成型的非匀质混合料，其拉压模量具有显著的差异，而我国现行路面设计方法仍采用基于拉压模量相等的经典线弹性理论，导致设计结果与实际路面受力状态存在较大偏差。为此，本项目选取典型路面材料—沥青混合料，以建立其考虑拉压模量差异的双模量本构方程及疲劳损伤方程为目标，通过室内力学性能试验研究，揭示其应力应变之间拉压不同的非线性力学性质及弹性参数的非线性规律；基于应力应变的实测结果及基本力学原理（即要求本构矩阵为对称阵及拉压模量相等时能回退到线弹性本构），构建沥青混合料的双模量本构模型；然后基于双模量理论开展全正弦波形荷载下的梁弯曲疲劳试验，揭示考虑拉压模量不同特性的沥青混合料模量的疲劳衰变规律及建立基于刚度衰变的疲劳损伤方程，据此建立基于双模量理论的沥青混合料疲劳特性表征方法。其研究成果可为建立考虑路面材料拉压模量差异和路面结构拉压交替受力性质的力学计算及抗疲劳设计方法提供依据。

绝大部分路面材料的拉压模量均具有显著的差异，而我国现行路面设计方法仍采用基于拉压模量相等的经典线弹性理论，导致设计结果与实际路面受力状态存在较大偏差。为此，本项目选取典型路面材料—沥青混合料，以建立其考虑拉压模量差异的双模量本构方程及疲劳损伤方程为目标，通过室内力学性能试验研究，揭示其应力应变之间拉压不同的非线性力学性质及弹性参数的非线性规律；基于应力应变的实测结果及基本力学原理，构建沥青混合料的双模量本构模型；然后基于双模量理论开展全正弦波形荷载下的梁弯曲疲劳试验，揭示考虑拉压模量不同特性的沥青混合料模量的疲劳衰变规律，主要取得以下结论：.1) 沥青混合料应力应变特性存在明显的拉压双线性特征，不同影响因素下材料的拉压模量及拉压泊松比具有良好稳定的相互关系，其中Ec/μc与Et/μt之间偏差在7%以内，验证了双模量理论的柔性矩阵对称性假定公式(Ec/μc=Et/μt)。.2) 沥青混合料拉压强度、拉压模量及拉压泊松比与加载速度、沥青含量及温度等因素均呈良好稳定的函数相关关系，据此建立了多因素作用下沥青混合料的拉压力学参数取值模型。.3) 沥青混合料最优判别法则为主应力判别法则，最优双模量本构模型为该法则下的Ambartsumyan本构模型。.4) 基于迭代思想建立了双模量沥青路面结构数值计算方法，且力学分析表明：基于双模量理论与基于传统线弹性理论的路面结构力学响应计算结果之间的偏差高达50%。.5) 拉压模量的差异特性对沥青混合料强度与疲劳测试结果的影响显著，并构建了基于双模量理论与基于传统线弹性理论力学参数测试结果之间的相关关系式。.6) 全正弦波形与半正弦波形荷载下沥青混合料的疲劳测试结果差距较大，并建立了其直接拉伸模量和真实四点弯曲模量的疲劳损伤模型及拉压交替荷载作用下直接拉伸模量的疲劳损伤模型，基于此构建了基于双模量理论的沥青混合料疲劳特性表征方法。.本项目研究成果可为基于双模量理论的耐久性沥青路面设计及参数取值提供依据。