Pavement Structural Condition Assessment using Deflection Basin Parameters

Abstract

Evaluating the structural integrity of high-traffic road networks is essential for effective pavement management, particularly in regions like Central Java, Indonesia. This study provides a comprehensive structural condition assessment by integrating Falling Weight Deflectometer deflection basin analysis with backcalculated layer moduli to identify subsurface weaknesses. The methodology focused on 5.9 km of the Surakarta–Sukoharjo road, comparing existing flexible pavements with recently widened sections. Deflection data were normalized to a standard 40 kN load and 41 °C temperature, then backcalculated using BAKFAA software to estimate the elastic moduli. The iterative algorithm targeted high precision, aiming for root-mean-square error values within the optimal range of 1% to 2%. Structural performance was quantified using indices: the Base Layer Index, Middle Layer Index, and Lower Layer Index for the asphalt, base, and subgrade layers, respectively. Results demonstrate that widened sections incorporating cement-treated bases exhibited significantly superior structural health compared with existing sections. Backcalculated moduli for asphalt concrete in widened segments (2,100–13,900 MPa) were approximately 2.8 times higher than those in existing segments (900–4,300 MPa). Furthermore, the cement-treated base layers achieved exceptionally high stiffness, with moduli ranging from 20,400 to 60,355 MPa, effectively mitigating vertical compressive strains at the subgrade.