路面加铺后旧沥青混合料的疲劳性能

针对老路面沥青层在加铺前后的不同受力状态,提出了两级荷载疲劳试验研究加铺后老路面沥青混合料疲劳性能的思路.通过小梁试件的室内两级荷载疲劳试验,获得了几种常用沥青混合料的二次疲劳方程,并在考虑室内与野外疲劳寿命差异的基础上,建议方程修正系数取1200.推荐了老路沥青层混合料抗拉强度结构系数供加铺设计参考.研究表明:沥青混合料二次疲劳方程与常规一级荷载疲劳方程具有相同的型式,且两者疲劳曲线的斜率没有变化,但由于一级荷载损伤的不同,二次疲劳曲线的位置有不同程度的下移;推荐的老路沥青层混合料抗拉强度结构系数克服了现有规范中沥青混合料抗拉强度结构系数不能用于老路沥青层底拉应力验算的缺陷,可直接用于加铺层设计或验算.

Fatigue performance of old pavement asphalt mixtures after overlay

Based on the different states of old pavement mixtures before and after overlay,fatigue tests with two-amplitude loadings in laboratory are advanced to research the fatigue performance of old pavement mixtures after overlay.The fatigue function of widely-used mixtures between fatigue life and the value of repeated strain was set up after fatigue test.Considering the difference of fatigue life between laboratory and field,the fatigue function was multiplied by 1200 to forecast the remnant life of old pavement after overlay.In order to apply fatigue equation to the design of overlay,tensile strength structure coefficient was recommended.The results show that fatigue function of the second-amplitude loading has the same formation and slope as fatigue function of single-amplitude loading which was often studied in the past.However,intercept of fatigue function of the second-amplitude loading is less than that of single-amplitude loading due to damage by the first-amplitude loading.Tensile strength structure coefficient recommended can be used to check the tensile stress of old asphalt pavement directly,which overcomes a deficiency in current specification.