Abstract: The properties of the granular debris deposits at upper portion of the coral reef and island have critical influence on the development of these reefs and islands. The strength and compressibility of the calcareous sand samples collected from the development of a coral reef were laboratory tested by using large scale direct shear device and the high pressure oedometer. The results indicated that, under the similar grain size distribution, the apparent cohesion value is effected by the rate of shearing and the content of coarse grains 9P5). Large shearing rate results in a smaller apparent cohesion value, whereas, the increase of P5 leads to an increase of apparent cohesion. The compressibility of the coral sandgravel mixture is impacted by the gravel composition and the quantity of the sand. At the same time, the moisture content of the mixture will affect the compressibility.

Key words: Coral SandGravel Mixtures, Direct Shear Test, High Pressure Consolidation Tests