Laboratory Plate Loading Test on Calcareous Sands from a Hydraulic fill Reef Island

The landforms and vertical strata distribution characteristics of Yongxing Island show that the reclaimed reef island is characterized by soft upper strata (calcareous sand) and hard lower strata (reef limestone). In this study, a series of plate loading tests was conducted to examine the influences of particle gradation, compactness, and moisture condition on the bearing mechanism and deformation properties of the calcareous sand foundation. When the foundation is shallowly buried, the relative density range corresponding to a calcareous sand foundation exhibiting local shear failure is narrower than that of a terrigenous sand foundation. For the same compactness, dry calcareous medium sand has a much larger bearing capacity and deformation modulus than dry calcareous fine sand. The effect of water on the bearing capacity of the calcareous medium sand is greater than the effect on calcareous fine sand. Its weak cementation and low permeability make the initial deformation of saturated calcareous fine sand slightly smaller than that under dry conditions. The stress dispersion angle of the calcareous medium sand foundation is 52°, which is larger than that of terrigenous sand. A larger stress dispersion angle leads to a higher bearing capacity and deformation modulus than those of terrigenous sand.