不同渗流形态下沥青路面结构动力响应分析

为了研究荷载-渗流耦合作用下不同渗流形态对沥青路面结构各力学场量响应的影响，进一步揭示沥青路面水损害机理，在高水压沥青混合料渗透试验的基础上，采用非线性有限元方法，模拟分析碗形分布动荷载下Forchheimer非线性渗流和达西线性渗流时饱水沥青路面内部各力学场量的变化。渗透试验结果表明：在较高水力梯度下渗流流速-水力梯度关系呈现出非线性特征，不再适用达西定律，而需应用Forchheimer非线性渗流定律描述。数值模拟分析结果表明：2种渗流形态时沥青路面结构内部各力学场量均随着车轮动荷载的作用过程表现出波动性，且孔隙水压力均随着半正弦波型荷载的变化而呈正相关关系；与达西渗流时计算结果相比，非线性渗流时上面层内正孔隙水压力的峰值高49%，沥青面层内水平方向的拉应力、压应力、拉应变的峰值分别高16%、105%、15%，且在路表产生竖向拉应力，孔隙水压力也远高于现场实测值；2种渗流形态时均在上基层底部产生竖向拉应力，在沥青路面内产生的剪应力差别很小。因此，在车轮动荷载作用下，饱水沥青路面内部形成超高孔隙水压力和高流速的非线性渗流，会产生比线性渗流更为严重的水损害，以往基于达西定律的饱水沥青路面动态响应分析低估了车轮动荷载对沥青路面水损害的影响程度。

Analysis of Dynamic Response of Asphalt Pavement Structure Under Different Seepage Flow States

In order to study the effects of different seepage states on the response of mechanical field parameters of asphalt pavement structures under load-seepage coupling behavior, and reveal the mechanism of water damage, this study simulated and analyzed the changes in the mechanical response of saturated asphalt pavement structures under Forchheimer seepage flow and Darcy seepage flow conditions using non-linear finite element method based on the permeability test of asphalt mixture under the condition of high water pressure. The permeability test results show that the relationship between seepage flow velocity and hydraulic gradient takes on the stronger nonlinear properties at higher hydraulic gradients, therefore Darcy's law is no longer active, but Forchheimer's nonlinear seepage flow can describe the nonlinear properties effectively. The simulation results show that the mechanical field parameters of asphalt pavement structures fluctuate with vehicle load both in Forchheimer and Darcy seepage flow conditions, and pore-water pressure has a positive correlation with half-sine wave load. Comparison of the calculated results using Darcy's law and Forchheimer's law for nonlinear seepage flow show that the positive pore pressure peak in the upper layer is 0.49 times higher, whereas the peaks of horizontal tensile stress, press stress, and tensile strain are 16%, 105%, and 15% higher, respectively. The vertical tension stress emerges at the surface of the pavement. The pore-water pressure peak at the surface course is much higher than the field measurement values. The vertical tension stress appeared at the bottom of the upper base course both in Forchheimer and Darcy seepage flow conditions. The difference between the shear stress peaks that appeared in each layer of asphalt pavement structures is not significant. Therefore, the water damage caused by nonlinear seepage flow, which can lead to ultrahigh pore-water pressure and high flow velocity in saturated asphalt pavements, is more serious than that caused by linear seepage flow. Previous dynamic response analysis of saturated asphalt pavements based on Darcy's law underestimated the influence of the degree of water damage caused by wheel dynamic load.