Investigating fracture damage evolution in semi-flexible pavement materials: a nonlinear dynamics analysis of acoustic emission signals

Semi-flexible pavement (SFP) exhibits complex fracture behavior due to its strong heterogeneity and temperature-dependent viscoelastic performance. This study investigates the damage mechanisms of SFP via nonlinear dynamics analysis of acoustic emission (AE) counts, considering the effects of temperature and interfacial modification with a silane coupling agent (KH550). Fracture tests were conducted with AE monitoring, and nonlinear metrics including approximate entropy, largest Lyapunov exponent, correlation dimension, Higuchi fractal dimension, Hurst exponent and power-law exponent were employed for characterisation, with principal component analysis (PCA) applied to elucidate the inter-parameter relationships. Results show that temperature significantly modulates AE signal features: the mean AE count of unmodified SFP decreases from 43.7 to 6.2 as temperature increases from −10 to 25 °C, and the power-law exponent α peaks at 3.93 at 0 °C, indicating that damage dominated by small-scale distributed microcracking. PCA confirms temperature as the dominant source of variation. KH550 effectively enhances interfacial bonding, reducing the mean AE count by 45.5% and kurtosis by 64.9% at −10 °C, and increasing the power-law exponent by 8.9% at 25 °C. PCA further reveals that the modifier primarily influences damage persistence rather than the core complexity–chaos balance.