Prediction on Residual Life for Existing Asphalt Pavement Based on SCB and 3D-DIC Technique
Accurately evaluating the residual life of the asphalt pavement of the over-service period expressway is essential to formulate pavement utilization strategies in reconstruction and expansion projects.27 asphalt concrete core specimens are drilled from the expressway with a service period of more than 20 a and made into 54 semicircular specimens,and the semi-circular bending(SCB)fracture and fatigue tests are performed to evaluate the fatigue resistance and residual life of the existing asphalt concrete pavement.In order to solve the problem that traditional test methods cannot capture the surface crack expansion of asphalt concrete specimens in high cycle fatigue test in real-time,stereo digital image correlation technology 3D-DIC is introduced to monitor the evolution trend of the strain field and crack length on the surface of asphalt concrete specimens with the number of fatigue loads.In addition,the change of crack length in the DIC image corresponding to each fatigue load cycle is effectively calculated by combining the K-d tree algorithm.Meanwhile,the bilinear softening cohesive zone model(CZM)is used to determine the strain threshold of asphalt concrete cracks,thereby ensuring the accuracy of the K-d tree algorithm to calculate the crack length.The Paris equation master curve is constructed to eliminate the inconsistency of cracking parameters of asphalt concrete under different stress ratios,and to characterize the fatigue resistance performance of asphalt concrete of various road sections within a wide load range.The result shows that(1)the strain threshold of asphalt concrete crack is 1980 με;(2)with the increase of stress ratio,the Paris equation parameters A and n show trends of increasing fluctuation and steady decline respectively,while the threshold of stress intensity factor increases steadily;(3)the residual lives of the asphalt surface of section K84,K124 and K165 are 2.13E+08,3.57E+08 and 1.02E+07 respectively.Except section K165,the residual fatigue lives of other road sections meet the design expectations of the long-life pavement.
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