Investigation of shear mechanical behaviors of geogrid-coral sand interfaces

Geogrid-reinforced coral sand (GRCS) effectively enhances the strength and stability of marine geo-structures in island and coastal areas. The complex interaction and underlying mechanism of the geogrid-coral sand interface potentially determine the mechanical properties of the GRCS. In this study, large-scale interfacial shear tests were carried out to investigate the mechanical behaviors of geogrid-coral sand interfaces under the coupled influence of grain size, geogrid properties, and stress level. Comparisons with siliceous sand indicate that the mechanical properties of the geogrid-coral sand interface are excellent but suffer from more complex influences originating from particle properties. The interfacial friction angle is more sensitive to grain size, whereas the pseudo cohesion is more sensitive to aperture properties. The shear interface shows a general evolution trend of "contraction-dilation-contraction", with the maximum and final dilation becoming more prominent as the aperture size and stress level decrease. The increase in grain size, vertical stress and geogrid apertures induces a thicker interface with more particle crushing. Given the microscopic geogrid-coral sand interaction, the force characteristics of the aperture are further analyzed, and an equivalent additional stress calculation method is developed to quantitatively characterize the effects of grain size, geogrid properties, and stress level.