Abstract: This project planed to investigate the brittleness index of coral reef limestone which is an important property of rock materials. For this purpose, physical property test, uniaxial and triaxial compression tests were performed on four types of reef limestone core samples (framestone, bindstone, rudstone and bioclastic limestone) which were sampled in a certain depth from a certain coral reef in South China Sea. The test results show that the physical and mechanical properties of reef limestone are strongly influenced by the fabric and diagenesis. The failure characteristics of reef limestone can be accurately described by the brittleness index which is calculated based on the relative magnitude and the absolute velocity of post peak stress dropping. The investigation also suggests that the brittleness index is sensitive to the confining pressure and decreases with the increase of confining pressure. Meanwhile, under uniaxial compression, the brittleness index of bioclastic limestone with low-porosity is similar to that of cement mortar, and higher than that of framestone and bindstone. Furthermore, with the increase of porosity, the brittleness indexes of rudstone and bioclastic limestone decrease, and the saturated uniaxial compressive strength is negatively correlated with porosity.

Key words: coral reef limestone, brittleness index, stress-strain curve, confining pressure, porosity