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为了定量表征与分析在疲劳荷载和冻融循环耦合作用下路面混凝土内部裂缝的演化规律,采用SEM与形态学图像分割法对不同疲劳荷载和冻融循环耦合阶段的混凝土微裂缝进行提取,采用Image-Pro Plus对微裂缝进行量化,采用灰色关联法研究了裂缝特征参数与耦合作用后路面混凝土弯拉强度损失的相关性。分析结果表明:路面混凝土内部存在平均宽度为13μm、最大长度为144μm的原始微裂缝,耦合作用下裂缝的演化沿长度方向为延伸和断裂交替变化,沿宽度方向为扩张和收缩交替变化,混凝土破坏时裂缝最大长度达到352.64μm,裂缝平均宽度达到15.4μm;当冻融循环150次时,裂缝面积密度显著增大,与原始微裂缝相比,混凝土破坏时裂缝面积密度增大了6.7倍;耦合作用下路面混凝土裂缝分形维数、平均宽度、最大长度与弯拉强度的相关性较高,灰色关联度分别为0.957、0.954、0.871;通过回归分析建立了路面混凝土弯拉强度损失与裂缝结构参数之间的方程,弯拉强度损失与裂缝分形维数、平均宽度、最大长度之间存在较好的线性相关性,相关系数达到0.97。
In order to quantitatively characterize and analyze the evolution of internal cracks in pavement under the coupling of fatigue load and freeze-thaw cycles, SEM and morphological image segmentation method were used to extract microcracks of concrete with different fatigue loading and freeze-thaw cycles. -Pro Plus to quantify the microcracks. The correlation between the crack characteristic parameters and the flexural strength loss of pavement concrete after coupling was studied by using gray correlation method. The results show that the original microcracks with the average width of 13μm and the maximum length of 144μm exist in the pavement concrete. The evolution of the cracks alternates along the length direction and alternates with the fracture along the length direction, alternately with the expansion and contraction along the width direction, and the concrete is damaged When the freeze-thaw cycle 150 times, the crack area density increased significantly, compared with the original micro-cracks, the crack area density increased by 6.7 times when the concrete was broken; the maximum length of the cracks reached 352.64μm, the average width of cracks reached 15.4μm; The fractal dimension, the average width and the maximum length of the concrete pavement cracks have a high correlation with the bending strength under the action of the gray correlation degree of 0.957, 0.954 and 0.871 respectively. The bending strength loss and the crack structure parameters of pavement concrete are established by regression analysis There is a good linear correlation between the loss of bending strength and the fracture fractal dimension, the average width and the maximum length, and the correlation coefficient reaches 0.97.