基于压-直剪试验的沥青路面层间剪切疲劳特性

Characterization of interface shear fatigue in asphalt pavement based on direct shear test with vertical loading

为探讨沥青路面在车辆荷载作用下的层间剪切疲劳特性,利用自主研发的压-直剪试验加载装置,对含层间界面的沥青混合料复合小梁进行层间压-直剪剪切疲劳寿命测试。通过改变3种环境温度(25℃、35℃、45℃)、2种黏层油用量(0.3、0.5 L/m^2)、5种剪切应力水平(0、0.03、0.06、0.1、0.2 MPa)及4种压应力水平(0.16、0.18、0.2、0.22 MPa)等试验条件,研究上述因素对复合小梁试件层间剪切疲劳寿命的影响规律。研究结果表明:随着温度升高,在25℃~45℃区间,0.3、0.5 L/m2黏层油用量下的层间疲劳寿命平均降幅分别为47.12%、72.79%,黏层油用量较多时层间剪切疲劳寿命对温度变化更敏感;随温度升高,在相同温度梯度内,相对常温区间段[25℃,35℃)小梁层间剪切疲劳寿命的变幅大于相对高温区间段[35℃,45℃];随着压应力水平增大,层间剪切疲劳寿命也逐渐增大,但其增大趋势随着温度升高逐渐减弱,当温度为45℃、压力0.2 MPa时,层间疲劳寿命仅521.8 s;随着剪切应力增大,在25℃、35℃、45℃条件下,层间剪切疲劳寿命下降速率(分别为k1、k2、k3),存在k2>k1、k2>k3的关系,且常温(25℃)状态下剪切应力对层间剪切疲劳寿命的影响不明显,而高温(45℃)状态下层间剪切疲劳寿命整体水平较低,剪切应力增大时其层间剪切疲劳寿命衰减效果也不明显。

In order to study the interlayer shear fatigue characteristics of an asphalt pavement under vehicular loading, the shear fatigue life of double-layered composite asphalt beam samples with an interface was tested, and a loading device that independently developed for compression-direct shear test was used. By change the factors of three test temperatures(25 ℃, 35 ℃, 45 ℃), two tack coat dosages(0.3, 0.5 L/m^2), five shear stresses(0, 0.03, 0.06, 0.1, 0.2 MPa) and four types of compressive stress levels(0.16, 0.18, 0.2, 0.22 MPa),the influence of the above factors on the interface shear fatigue life of composite beam samples was studied. The results show that as the temperature increases from 25 ℃ to 45 ℃, the interlayer shear fatigue life reduces by 47.12% and 72.79%, when 0.3 and 0.5 L/m2 tack coat dosages are applied, respectively. Further, the interface shear fatigue life is more sensitive to temperature changes when the dosage of the tack coat is higher. The variation in the fatigue life at an intermediate temperature range [25 ℃, 35 ℃) is larger than that at the high temperature range [35 ℃, 45 ℃]. As the compressive stress level increases, the interface shear fatigue life increases gradually. However, the increasing trend gradually decreases with temperature increasing. When the temperature reaches 45 ℃ and the compressive stress is 0.2 MPa, the interlayer shear fatigue life is only 521.8 s. The failure rate of the interface shear fatigue life at 25 ℃, 35 ℃, and 45 ℃ is k1, k2, and k3, respectively. When the shear stress increased, the failure rate ranked as k2>k1 and k2>k3. Furthermore, the effect of shear stress on the interface shear fatigue life was not obvious at normal temperatures(25 ℃), but at the high temperature condition(45 ℃), the overall level of the interlayer shear fatigue life was lower, and the attenuation effect of the interlayer shear fatigue life was not obvious when the shear stress increased. 3 tabs, 6 figs, 27 refs.