Ling Zeng

Highway embankments with carbonaceous mudstone fill material are prone to deformation and instability under traffic loading and rainfall owing to particle breakage-induced stiffness and strength degradation. This study aims to investigate the particle breakage characteristics of carbonaceous mudstone fill material under dynamic loading with prior seepage conditioning, and to establish a permeability model considering breakage behaviour. To this end, a custom-designed testing apparatus was employed to conduct dynamic loading and permeability tests on specimens with varying coarse particle content (CPC) under different dynamic loads and seepage durations. Changes in particle size distribution, average saturated permeability coefficient and relative breakage ratio were analysed, and a permeability model relating the coefficient to the breakage ratio was proposed. The results indicate that the dynamic loading-affected range in the upper part of the specimens increases with higher CPC and greater loading levels. When CPC is below 40%, permeability changes little, whereas significant local variation occurs at higher CPC. A threshold dynamic load of 40 kPa, particularly at a CPC of 40%, was identified as the condition that triggers particle breakage and induces abrupt changes in seepage behaviour. The developed model effectively captures the nonlinear relationship between permeability and relative breakage ratio.

Coatings that are tolerant of poor surface preparation are often used for rapid, real-time maintenance of aging steel surfaces. In this study, a modified epoxy (EP) anti-rust coating was proposed, utilizing methyl gallate (MG) as a rust conversion agent, graphene oxide (GO) as an active functional material, and epoxy resin as the film-forming material. The anti-rust mechanism was investigated using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and the scanning vibration electrode technique (SVET). The results demonstrated that over a period of 21 days, the impedance of the coating increases while the corrosion current density decreases with prolonged soaking time. The coating exhibited a maximum impedance of 2259 kΩ, and a lower corrosion current density of 8.316 × 10⁻³ A/m², which demonstrated a three-order magnitude reduction compared to the corrosion current density observed in mild steel without coating. LSCM demonstrated that MG can not only penetrate the tiny gap between the rust particles, but also effectively convert harmful rust into a complex. SVET showed a much more uniform current density distribution in the micro-zones of mild steel with the anti-rust coating compared to uncoated mild steel, indicating that the presence of GO not only enhanced the electrical conductivity of the coating, but also improved the structure of the coating, which contributed to the high performance of the modified epoxy anti-rust coating. This work highlights the potential application of anti-rust coating in the protection of metal structures in coastal engineering.