Abstract：Mechanical properties of calcareous rock become one of the new research issues in geotechnical engineering while embarking upon ocean resources exploitation and marine works construction. Physico- mechanical properties of calcareous rock samples，which are taken from Yongshu and Zhubi coral reefs in Nansha Islands in South China Sea，are tested. The tests include ultrasonic wave test，uniaxial tensile strength test，uniaxial compression strength test，and triaxial compression strength test. The results show that the porosity of calcareous rock is much larger than that of other rocks；and the longitudinal elastic wave velocity is linearly decreased with the increase of porosity. Longitudinal elastic wave velocity is between 2 700 m/s and 3 700 m/s. The difference of dry and saturated tensile strengths is not evident；and the results show that the strength of calcareous rock does not decrease when it is saturated by water. Calcareous rock is brittle but it is different from granite. Multi-fracture planes emerge along the growth line of coral when breakdown occurs and it keeps considerably high residual strength. It is found that the damage pattern is determined by lithologic frame of calcareous rock.
