Study of the Mechanical Properties of Coral Reef Sand Mixes Using Large-Scale Triaxial Shear Tests

In order to reveal the macro-mechanical characteristics of coral reef sand mixes, triaxial tests were conducted on graded coral reef sand mix specimens using a large dynamic triaxial instrument. Under different circumferential pressures, the specimens’ stress–strain relationship curves showed a typical hyperbolic curve. Upon reaching peak stress, the specimens continued to develop axial strain with little change in principal stress difference. After damage, the radial strain-axial strain curve becomes straight. Under different peritectic pressures, all specimens experienced shear contraction followed by shear expansion. The strength of the coral reef sand is mainly derived from the combined effect of reef sand strength, inter-particle friction and occlusion, without the effect of cohesion. The initial particle filling determines the deformation and strength characteristics of the material in the test, while shear expansion (shear contraction), particle fragmentation and rearrangement, and volume changes influenced by the surrounding pressure are all manifestations of the changing interparticle filling relationship.