不同结构类型珊瑚礁灰岩弹性波特性研究

基于岩石弹性波特性的地震方法是目前地球物理勘探中最主要的方法，岩石中弹性波传播速度是联系岩石物理力学特性与地质学的有效桥梁。对于海相生物成因的珊瑚礁灰岩而言，其弹性波特性研究是了解珊瑚礁体内部整体性质的有效途径。研究表明，珊瑚礁灰岩的弹性纵波速度与干密度、回弹值呈线性正相关关系，与孔隙度呈线性负相关关系。不同结构类型珊瑚礁灰岩弹性波特性表现出显著的差异性，珊瑚骨架灰岩和珊瑚砾块灰岩均匀性较好，珊瑚砾屑灰岩和珊瑚砂屑灰岩离散性较大。基于珊瑚礁灰岩纵波速度与干密度、孔隙度以及回弹值之间的关系，结合某珊瑚礁体钻孔岩芯沿深度变化的回弹值信息以及岩芯薄片光学检测结果，提出一个基于纵波速度的珊瑚礁灰岩质量等级的划分标准，具有一定的可靠度和适用性。运用岩石二相体模型基本原理，建立了修正的时间平均公式，而不同结构类型珊瑚礁灰岩弹性波特性均符合雷莫亨特-加德纳方程。

Elastic wave properties of coral reef limestone with different structural types

The seismic method based on elastic wave characteristics of rock is the most important method in geophysical exploration. The propagation velocity of elastic wave in rock is an effective bridge connecting physical and mechanical characteristics of rock with geology. In terms of biogenetic coral reef limestone in the sea, the characteristics of elastic wave is an effective way to find out the whole internal properties of coral reef. This study shows that the elastic longitudinal wave velocity of coral reef limestone has a linear positive correlations with dry density and rebound value, but has a linear negative relationship with porosity. The elastic wave features of coral reef limestone with various structural types present significant difference. For example, coral skeleton limestone and coral gravel limestone have good uniformity, whereas coral gravel limestone and coral sand limestone have distinct dispersion. Based on the relationships between longitudinal wave velocity and dry density, porosity and rebound value of coral reef limestone, a classification standard of the quality grade is proposed for coral reef limestone, combined with the rebound values of drilling core along the depth of a coral reef and the optical detection results of core sheets. It has certain reliability and applicability. A modified time-average formula is established by using the basic principle of two-phase rock model. In addition, Remo Hunter-Gardner equation is suitable for elastic wave characteristics of coral reef limestone with different structural types.