Abstract: To mitigate the frequent storm surge disasters in the South China Sea, this study proposes the construction of a gabion-armored and geosynthetic-reinforced coral sand sea dike utilizing locally abundant coral sands within the marine area. This approach offers several advantages, including environmental sustainability, low carbon footprint, ease of construction, high stability, and cost-effectiveness, demonstrating broad application prospects. Large-scale wave flume experiments were conducted to investigate the dynamic response characteristics and stability of gabion-armored and geosynthetic-reinforced coral sand sea dike under 50-year return period wave conditions in the South China Sea. The results indicate that the sea dike exhibits excellent stability under tested wave conditions, with the maximum vertical deformation at the crest accounting for only 23.2% of the allowable value in the relevant code. The positive wave pressure on the slope decreases from the toe to the crest, while the negative pressure first decreases and then increases along the same direction. The gabion armors enhance wave breaking, resulting in a reduction of both positive and negative wave pressures on the upper slope. Alternating positive and negative pore pressure oscillations are observed on the offshore side within the dike, while the amplitude of pore pressure oscillations decreases on the far offshore side, albeit with a small amount of accumulated pore pressure. The maximum pore pressure remains significantly lower than the effective stress at the corresponding depth, indicating that liquefaction does not occur in the sea dike. The geogrid undergoes periodic tensile and compressive states, with an average cycle of approximately 24 s, 7.6 times the wave period. The maximum tensile strain experienced by the geogrid is 0.21%, which is below the typical strain range for geogrids in land-based reinforced structures under working stress conditions.

Key words: coral sand, sea dike, reinforced soil structure, wave flume test, storm surge disaster, dynamic response