Abstract: As the main raw material for marine engineering construction, coral sand with high calcium carbonate content is porous and fragile. In order to further accelerate the construction of marine engineering and improve the strength and stability of geo-structures, using geogrid to reinforce coral sand is a potentially effective means. In present study, a series of triaxial tests was conducted to investigate the effects of the number of geogrid layers, initial water content, and confining pressure on the strength and deformation of geogrid-reinforced coral sand. The results indicate that the geogrid reinforcement can obviously improve the mechanical properties of coral sand. With increasing number of geogrid layers, the overall strength of the reinforced coral sand gradually increases. The stress-strain relationship shows a general hardening trend, and the lateral bulging is also restrained effectively. Similarly, the introduced pseudo-cohesion increases linearly with increasing number of geogrid layers, and the internal friction angle decreases slightly. As the initial water content increases, the strength of geogrid-reinforced coral sand decreases slightly, and the pseudo-cohesion changes little. However, the internal friction angle decreases by about 4º compared with the drying condition. The particle breakage of geogrid-reinforced coral sand is greatly affected by confining pressure in triaxial case, and the relative breakage rate below 400 kPa confining pressure is mainly less than 3%. Additionally, the lateral and axial additional stresses are considered and calculated by analyzing the geogrid-sand interfacial characteristics. These results further enrich the understanding of the mechanism of geogrid-reinforced coral sand.

Key words: geogrid, coral sand, triaxial test, mechanical properties, deformation behavior