Abstract: The at-rest lateral earth pressure coefficient is an important soil parameter that indicating the relationship between the vertical and lateral stresses in the soil mass and poses an important role throughout every aspect of geotechnical engineering. The coral sand is a unique geotechnical material with a relatively low individual grain strength and welldeveloped angularity, therefore, the engineering properties of the coral sands are significantly different from those of quartz sand of land origins. This paper presents the laboratory at-rest lateral earth coefficient test results of coral sand samples under various relative density and moisture contents throughout the Anteus high-pressure consolidation test devices. The results indicated that: 1) the tested at-rest lateral earth pressure coefficients are between 0.20 and 0.29 and these values are smaller than those of from quartz sand samples. 2) The at-rest lateral earth pressure coefficient of coral sand samples increases with the moisture content, but the increment is not significant. 3) The effect of density of samples on the magnitude of lateral earth pressure is not significant.

Key words: Medium Coral Sands, At-Rest Lateral Earth Pressure Coefficient, Anteus High Pressure Consolidometer, Relative Density, Moisture Content