砂质海底沉积物压缩波速与物理参数关系试验研究  

Experimental study on the relation between compressional wave velocity and physical properties of sandy sediments

作　　者：王虎 吴涛 张仕杰 孙振银 周亚迪 朱涛 WANG Hu;WU Tao;ZHANG Shijie;SUN Zhenyin;ZHOU Yadi;ZHU Tao(School of Marine Science and Technology,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学海洋科学与技术学院,天津300072

出　　处：《海洋地质与第四纪地质》2021年第2期222-230,共9页Marine Geology & Quaternary Geology

基　　金：山东省海洋生态环境与防灾减灾重点实验室开放基金项目“基于声学遥测的近海底质精细化识别研究”(201805);国家级大学生创新训练计划项目“海底粉土声传播规律试验研究”(201810056104);国家自然科学基金项目“基于波致动力固结的黄河三角洲铁板砂形成过程研究”(41702307)。

摘　　要：砂土是主要的海底沉积物类型之一,明确砂质沉积物声学与物理性质的关系对海底底质和地层探测至关重要。本文利用超声探测仪和自制的试样制备测试装置,模拟制备不同沉积状态的砂土试样,同步开展超声测试和物理性质测试,探讨砂质沉积物声速测试方法及影响因素,揭示砂质沉积物压缩波速与物理参数的内在联系。试验结果和分析表明:换能器接触管壁的间接测量方法中,声波多路径传播可显著影响沉积物声速测量的准确性,而换能器接触试样的直接测量方法可避免这一影响;30 kHz至100 kHz的不同频率对压缩波速测量结果没有明显影响。砂质沉积物的压缩波速与密度、孔隙度、含水率有较好的相关性,相关系数分别为0.87、0.86、0.84,并且随密度的增大而增大,随孔隙度、含水量的增大而减小。砂质沉积物的压缩波速与中值粒径的相关系数小于0.6,对物质组成不敏感。另外,与声速相比,砂质沉积物的声阻抗与密度、孔隙度、含水量的相关性更高。砂质沉积物压缩波速对饱和度非常敏感,例如,饱和度从0.971增至0.994时,压缩波速从393.3 m·s^(-1)急剧增大到748.5 m·s^(-1),需特别注意。Sand is one of the main type of submarine sediments.Figuring out the relation between acoustic and physical properties of sandy sediments is critical to seafloor and sub-bottom detection.In this paper,by using the ultrasonic detector and the self-developed sample preparation device,sand samples in different physical states are prepared to simulate different natural sedimentary conditions.Acoustic and physical properties are tested simultaneously,so as to reveal the effective measuring methods and its influence factors,and to explore the internal connection between the compressive wave velocity(CWV)and physical parameters of sandy sediments.Results and analysis indicate that the multipath propagation of sound wave can affect the measurement accuracy for the method with ultrasonic transducers touching the side wall of sediment container,while this effect can be avoided by measuring with a direct contact between transducers and sediment.No effects are found with different test frequencies among 30 kHz to 100 kHz.The CWV of sandy sediments,which shows good correlation with density,porosity and water content,with correlation coefficients 0.87,0.86,and 0.84,respectively,increases with increasing density,while decreases with increasing porosity and water content.While the correlation coefficient between CWV and medium diameter is smaller than 0.6,which shows that the CWV of sandy sediments has no clear link to grading distribution.The correlation of acoustic impedance with bulk density,porosity and water content is bigger than that of CWV with them.In addition,special attention should be paid to the saturation of sediments because the CWV is very sensitive to saturation,for example,the CWV increases dramatically from 393.3 m·s^(-1) to 748.5 m·s^(-1) as the saturation increases from 0.971 to 0.994.

关 键 词：海底沉积物 压缩波速 声阻抗 物理参数 

分 类 号：P733[天文地球—物理海洋学]