基于法标两阶段设计的复合式基层沥青路面结构力学分析

Mechanics Analysis of Composite Base Asphalt Pavement Structural base on Two Stages Design Method of French Norms

借鉴法国两阶段设计理念,结合复合式基层沥青路面常见破坏模式,选取力学响应指标;利用有限元软件建立塞内加尔MBOUR-KAOLACK(MK)高速公路复合式基层沥青路面的三维模型,分析半刚性底基层破坏前后两个不同阶段下路面结构力学响应的差异,探讨路面结构层厚度和模量对各力学指标的影响,进而分析各指标对路面结构层参数的敏感性。结果表明:在第一阶段时,沥青层层底拉应变远低于疲劳极限值;在第二阶段时,沥青层层底拉应变大幅度上升,故应视半刚性底基层情况分别选择路面疲劳开裂控制指标;在两阶段中,除沥青层顶面压应变外的其他指标均存在较大差异。半刚性底基层层底拉应力随着路面各层厚度和沥青层模量增大而降低,但随着底基层模量增大而增大,故底基层模量不宜过高;沥青层层底拉应变和路基顶面压应变随着路面结构层厚度和模量的增大而降低。此外,在两阶段中,与半刚性底基层层底拉应力、沥青层层底拉应变和路基顶面压应变相比,沥青层顶面压应力和最大剪应力对路面结构层参数的敏感性较低;值得注意的是底基层和基层厚度分别在两阶段中对疲劳控制指标的敏感度系数均最大,可见基层与底基层厚度的取值在复合式基层沥青路面结构设计中非常关键。

In this paper,mechanical response indexes are selected by referring to the two stages design method of French Norms and the common damage modes of composite base asphalt pavements.The threedimensional model of the composite base asphalt pavement of the MBOUR-KAOLACK(MK)highway in Senegal is established by using finite element software.Then the differences in the mechanical response of the pavement structure under two stages(before and after the damage of the semi-rigid subbase)are analyzed.The influence of pavement structural layer thickness and modulus on each mechanical index is explored,and then the sensitivity of each index to the pavement structural layer parameters is analyzed.The results show that in the first stage,the tensile stain at the bottom of asphalt layer is much lower than the limit fatigue value.In the second stage,the tensile strain at the bottom of asphalt layer increases significantly,so the fatigue cracking index of the pavement should be selected depending on the semi-rigid subbase state.Among the two stages,there are large differences in all indicators except for the compressive stress at the top of asphalt layer.The tensile stress of semi-rigid subbase decreases with the increase of the thickness of each pavement course and the modulus of the asphalt course,but increases with the increase of the modulus of subbase,so the modulus of the subbase should not be too high.The tensile strain at the bottom of asphalt layer and compressive strain at the top of subgrade decrease with the increase of the thickness and modulus of the pavement layer.In addition,the compressive stress at the top of asphalt layer and the maximum shear stress of asphalt layer are less sensitive to the pavement layer parameters compared with the tensile stress at the bottom of semi-rigid subbase,the bottom of asphalt layer,and compressive strain at the top of subgrade.It is worth noting that the sensitivity coefficients of base and subbase thickness are the maximum for the fatigue index in the two stages,which shows that the values of base and subbase thickness are very critical in the design of composite base asphalt pavements.