Coral gravel soils, which are composite soils consisting of finger-coral fragments and silt matrix, are often found in coastal regions of sub-tropical islands. In this study, for reconstituted soils with various coral gravel fractions up to 44% that was the densest package, a series of triaxial CU-bar and CD tests was conducted to study determination method for soil design parameters in consideration of interaction between soil skeleton consisted of coral fragments and silt matrix. The soil parameters were significantly influenced by volumetric percentage of coral fragments in association with particle interaction and particle crush, when the percentage was larger than 20% for the coral gravel soils examined in this study.