Evaluation Index of Pavement Structural Cracks Based on Deflection Response

To accurately assess the impact of structural cracks on the strength of pavement structures and establish corresponding evaluation indicators based on deflection response, field tests were conducted on multiple sections of expressways in Jiangsu Province. A falling weight deflectometer was used to test a total of 15 measurement points within a 3-meter range on both sides of each crack. The center deflection values at each measurement point were plotted into curves, and three evaluation indicators for cracks, namely deflection range, maximum influence distance on one side of the crack, and influence area, were proposed based on the characteristics of the curves. Core samples were taken directly above the selected cracks within the test sections to verify the crack types and development layers. According to the distribution and cracking conditions of the cracks in the core samples, six types of structural cracks were classified. The results show that the proposed indicators can effectively distinguish fatigue cracks from structural cracks. The coefficient of determination (R2) between deflection range and influence area is 0.75, and the Pearson correlation coefficient is 0.88. Both indicators have a good correspondence with the various stages of crack development and can be used in combination to evaluate the severity of cracks, providing practical guidance for pavement maintenance and construction.