Comprehensive Investigation on Mechanical and Breakage Behaviors of Coral Sand under Plane Strain State

Coral sand, as a critical fill material in island reef engineering, is often subjected to plane strain state, but its mechanical and breakage behaviors under such a condition has been rarely characterized. This study presents comprehensive plane strain tests on two grades of coral sand with some new features: (1) A true triaxial test apparatus was used with advantage of measuring the stress state in plane strain direction, based on which the evolution of intermediate principal stress coefficient (b-value) can be analyzed. (2) Beyond some conventional variables, loading direction and stress path were considered. Furthermore, triaxial compression and extension tests were also performed for comparison. After testing, the particle size distributions were measured to explore the law of particle breakage under plane strain state. The test results showed that in the plane strain compression tests, the b-values of coral sand at peak and critical states remained essentially independent of test conditions. Under both compression and extension loading conditions, coral sand exhibited higher shear strength under plane strain state compared to triaxial stress state. When coral sand specimens were loaded in the same direction, a unique relationship between relative breakage index and input energy was found under plane strain state.