南沙群岛珊瑚礁礁灰岩力学特性研究

RESEARCH ON CHARACTERISTICS OF CORAL REEF CALCAREOUS ROCK IN NANSHA ISLANDS

对取自南沙群岛永暑礁和渚碧礁的礁灰岩的物理性质和力学性质进行测试,包括声波测试、单轴抗拉强度试验、单轴抗压强度试验和三轴压缩强度试验。试验结果表明,礁灰岩具有较高的孔隙率,远远大于其他岩石,其纵波波速为2 700～3 700 m/s,并随着孔隙率的增大线性减小;礁灰岩的软化性较弱,干燥抗拉强和度饱和抗拉强度相差不大;礁灰岩的破坏形态表明其具有脆性岩石的特点,但又与花岗岩等脆性岩石有本质的区别。在破坏时并不像其他脆性岩石一样具有单一破裂面,而是沿着珊瑚生长线同时出现多个破裂面,并保持较高的残余强度,礁灰岩的这种破坏模式是由其特殊的岩体结构决定的。

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. Physicomechanical 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 pattem is determined by lithologic frame of calcareous rock.