Deterioration of skid resistance for ultra-thin asphalt overlay under the environmental conditions in highway tunnel

Despite being one of the most preferred methods for improving skid resistance in highway tunnels, the deterioration behaviour of ultra-thin asphalt overlays under tunnel conditions remains unclear. To address this issue, a tire-pavement contact model was developed to investigate the influence of water, oil, and particulate contaminants on the deterioration of skid resistance. The British pendulum tester, laser scanner, and contact stress test were employed to comparatively analyse the friction coefficient, texture characteristics, and stress contact states of skid resistance on ultra-thin asphalt overlay during the abrasion cycles with aforementioned influences. The results show that the oil film has the most significant influence on the deterioration of the skid resistance in ultra-thin asphalt overlays. After introducing the tunnel environment, the attenuation trend of the British pendulum number (BPN) becomes steeper. During the abrasion process, the surface mean texture depth (SMTD) and root-mean square deviation (Sq) decrease to varying degrees, while the root-mean square slope (Sdq) and peak summit density (Spd) increase, intensifying the dispersion of the stress distribution. Statistical analysis indicates that the correlation between Sq and the stress concentration rate (T) remains strong with BPN (>0.85), making them reliable predictive indicators for the skid resistance of ultra-thin overlays in highway tunnel.