声学特性参数定量反演海底沉积物粒度类型的理论与实验研究

By measurement of the parameters of the sediments, which were collected from the South China Sea, under laboratory conditions of temperature and pressure in situ, the data of acoustic properties, such as the longitudinal wave velocity, the acoustic impedance and acoustic attenuation, were inversed in light of the hydroacoustic data obtained on survey ship, mentioned above. Then elastic parameters, such as shear modulus of saturated sediments, shear modulus and bulk compressibility modulus of consolidation sediments, were inversed according to the data of acoustic properties above. At the same time, analysis results of sediment particle size can be accessed. So with the help of sound-complex variable model deduced by means of the basic acoustic theory, the basic formula of elastic modulus and the theoretical relationship between the elastic modulus and the volume fraction of each component of sediments, we can establish theoretical and empirical formula which may quantitatively inverse marine sediments porosity, consolidation shear modulus and bulk compressional modulus of consolidated sediments by acoustic parameters, and then establish theoretical and empirical formula which may quantitatively inverse the volume fractions in percentages of the three components that are sand, silt and clay of seafloor sediments by these acoustic parameters above. Furthermore we can identify the mass percentages of the sand, silt and clay, three components of the sediments, so the type of the sediment grain size can be denominated. Thereby we achieve the project target that establishes the system theory and experimental techniques by which inversion of type of grain size of seafloor sediment with the acoustic properties of seafloor sediment can be accomplished. This will have important theoretical significance and application value in cross-infiltration and integrated development of hydroacousticphysics, marine geology and oceanography military.

对采自南海海底沉积物样品，进行实验室中的海底温压条件下沉积物各项参数测量，获得纵波声速、声阻抗和声衰减等海上声学反演可以得到的声学特性参数数据；获得沉积物剪切模量、固结剪切模量、固结体积压缩模量等弹性参数，以及获得沉积物粒度分析数据。利用声学基础理论建立的声速-复合参数模型、弹性基础理论公式，以及沉积物弹性模量与各成分体积分数理论关系等，建立声学特性参数定量反演海底沉积物孔隙度、固结剪切模量、固结体积压缩模量等理论公式与经验公式，建立声学特性参数定量反演海底沉积物的砂、粉砂、粘土三组分体积分数的理论公式与经验公式方程组，进而求解和计算出沉积物的砂、粉砂、粘土三组分质量百分含量，以便对沉积物进行粒度类型定名。由此实现本项目研究目标：建立声学特性参数定量反演海底沉积物粒度类型的基础理论与实验技术。这对于海洋物理学、海洋地质学和海底声学物理等交叉渗透与融合发展，具有重要理论意义和应用价值。

海底沉积物声学物理和沉积粒度参数数据是国家海洋经济建设和海洋军事国防迫切需要的重要战略资源。用声学方法反演海底沉积物粒度类型，一直是海洋科学家的研究热点。所以，本项目进行“声学特性参数定量反演海底沉积物粒度类型的理论与实验研究”。.本项目研究声学特性参数与物理力学和沉积粒度参数的经验关系，研究海底沉积物纵波声速与弹性参数理论关系和经验公式，研究纵波声速与横波声速理论关系，研究海底沉积物纵波声速、横波声速及声速比求解弹性参数理论关系，研究海底沉积物弹性参数与粒度参数之间理论与经验关系，研究声学特性参数反演计算海底沉积物的砂、粉砂和粘土的粒度三组份体积分数和重量百分含量的计算方法。.经过四年的研究，获得了一些重要研究结果和关键数据：发现了海底沉积物在应力-应变过程中，其纵波声速随着静弹性模量增大而减小，在静弹性模量40MN/m2至50MN/m2之间声速取得最小值，然后声速随着静弹性模量增大而增大；建立了海底沉积物声速-双复合参数经验公式；建立了海底沉积物纵波速度与横波速度理论关系；建立了纵波声速与横波声速求解沉积物弹性参数理论公式；得到了沉积物横波声速小于0.86603倍纵波声速理论关系；得到了剪切模量小于0.86603倍体积压缩模量时，纵波声速与横波声速的关系可以表示为自变量是横波声速的泰勒多项式；发现了海底沉积物含砂量增大引起纵波速度增大的原因是含砂量增大引起沉积物体积压缩模量变化比的值大于密度变化比的值。这些重要研究结果和关键数据是本项目建立声学特性参数定量反演海底沉积物粒度类型的理论系统基本内核。.本项目研究获得的声学特性参数定量反演海底沉积物粒度类型的理论关系和经验公式，是建立海底地声模型的声学特性参数与物理力学参数、粒度参数关系的重要理论内核，对于高精度海底地声模型的建立、水声传播军事应用和海底水合物资源勘探开发等方面，具有重要理论意义和应用价值。