南沙海区珊瑚礁灰岩纵波波速特征及其影响因素

P-wave velocity properties and its influencing factors of coral reef limestone in Nansha area

珊瑚礁灰岩是孔隙结构复杂、密度变化较大的一类岩石,但过去对珊瑚礁灰岩纵波波速与孔隙结构的关系及其影响因素研究不够深入。本文测定和分析了南沙海区某岛礁钻孔中珊瑚礁灰岩的纵波波速、孔隙度以及密度特征,结果显示礁灰岩的纵波波速变化范围为5104~5958m·s–1,孔隙度变化范围为1.47%~17.7%,密度变化范围为2.07~2.72g·cm–3。这些特征表明,埋藏后的压实作用和重结晶作用,对珊瑚礁灰岩的孔隙度和密度产生影响。珊瑚礁灰岩弹性波速主要受孔隙度和孔隙结构类型的影响,礁灰岩横、纵波速比值能有效地确定岩体的结构和稳定性,因此礁灰岩的声学特性研究成果可为珊瑚岛礁工程建设的稳定性评估提供可靠的数据支撑。

Coral reef limestone is a kind of rock with complex pore structure and large density variation. The relationships between P-wave velocity and pore structure of coral reef limestone and the influencing factors on acoustic properties, however, are not well studied. The P-wave velocity, porosity, and density of coral reef limestone were measured and analyzed in this study. The results exhibited that the P-wave velocity of coral reef limestone varies between 5104 and 5958 m·s–1, its porosity varies between 1.47% and 17.7%, and its density varies between 2.07 and 2.72 g·cm–3. We showed that the porosity and density in coral reef limestone were determined by compaction and recrystallization. In addition, the porosity and pore structure also had an effect on P-wave velocity in coral reef limestone. More importantly, the structure and stability of coral reef limestone can be determined by the ratio of S-wave and P-wave velocities. The acoustic properties of coral reef limestone can provide important support for the stability of engineering.