中国科学院海洋研究所机构知识库

    海底沉积物作为水下声场的重要边界，其中低频声学参数对浅海复杂环境下声波传播规律和声场结构具有重要影响，在海洋地球物理探测，海洋声场测量与预报、海底埋藏物声学探测、水声通讯等领域均具有重要应用价值。

    本文选取胶州湾平坦潮滩作为大尺度中低频实验场地，利用国家海洋局第一海洋研究所的中低频测量设备、中高频原位测量系统对胶州湾海底浅表层沉积物进行原位声速测量，利用信号发生器、示波器等声学设备对胶州湾海底浅表层柱状沉积物样品进行室内声速测量，利用弯曲元剪切波测量设备对黄海海底柱状沉积物样品进行剪切波速测量，并测定了细粒沉积物（胶州湾柱状沉积物样品和黄海柱状沉积物样品）的孔隙度、密度、粒径等物理力学参数。

    将实验得到的沉积物声速与频率的相关关系进行分析，结果表明：频率越高，沉积物声速越大。频率小于1 kHz时，声速变化范围较小（声速增幅为3.2 %）；频率介于1~20 kHz之间时，声速变化范围较大（声速增幅为7.0 %）；频率大于20 kHz时，声速变化范围较小且趋于定值（声速增幅为3.0 %）。实测数据与指数拟合曲线符合度最好，其次是对数拟合曲线。

    结合Biot理论和Buckingham理论，对实测数据与理论模型的相关性进行分析，结果表明：频率小于20 kHz时，实测数据与Biot模型频散变化趋势一致，但实测声速值低于Biot模型预测值；频率大于20 kHz时，实测数据与Buckingham的GS模型符合度较好。

    结合物理力学参数，分析了剪切波实测数据与GS模型的相关性，结果表明：海底沉积物剪切波速度、孔隙度、平均粒径与GS模型预测趋势较为一致；海底沉积物埋藏深度对剪切波速影响较大，而测量频率（1~5 kHz）对剪切波速影响较小。

    本文对胶州湾海底沉积物进行了中低频（300 Hz~34 kHz）原位声学测量和中高频（25~250 kHz）实验室声学测量，对黄海海底沉积物柱状样品进行了剪切波速（1~5 kHz）测量。分析了细粒沉积物声速与物理性质的相关性，结合声传播理论，阐述了声波与频率的依赖关系。该研究对丰富海底声学理论，促进海底沉积物中低频声学参数及频散特征的深入研究具有一定的借鉴意义。

    Seafloor sediments as an important boundary of underwater acoustic field, its low-middle frequency acoustic characteristics have the important influence on the law of sound wave propagation and the sound field structure in shallow water, and have important application value in marine geophysical detection, Ocean acoustic field measurement and prediction, submarine burial acoustic detection and underwater acoustic communication.

    In this paper, the Jiaozhouwan beach was selected as the large scale low-middle frequency experimental site. And the low-middle frequency measurement equipment, the in-situ middle-high frequency measurement of the First Institute of Oceanography, State Oceanic Administration, were used to carry out the in-situ sound speed measurement. Acoustic equipment, such as signal generator and oscilloscope, were used to measure the sound speed of Jiaozhouwan seafloor shallow surface columnar sediment samples in the laboratory. The bending element shearing measurement equipment was used to measure the sound speeds of the Yellow Sea seafloor columnar sediment samples. And the physical and mechanical parameters such as porosity, density and particle size of fine grained sediments (Jiaozhouwan and Huanghai sediment samples) were measured.

    The correlation between the sound speed of sediment and the frequency is analyzed, and the results show that the higher the frequency is, the greater the sound speed become. When the frequency is lower than 1 kHz, the sound speed varies slightly (sound speed increases 3.2 %); when the frequency is between 1~20 kHz, the range of sound velocity become larger (sound velocity increases 7.0 %); when the frequency is greater than 20kHz, the sound speed varies slightly and tends to be a fixed value (sound speed increases 3.0 %). The conformance degree between the measured data and the exponential fitting formula is the best, followed by the logarithmic fitting formula.

    Combining the Biot theory with the Buckingham theory, the correlation between the measured data and the theoretical model is analyzed, and the results show that: When the frequency is lower than 20kHz, the tendency of the measured data is consistent with the tendency of the Biot model, but the measured sound speed value is lower than the predicted value of the Biot model. When the frequency is greater than 20kHz, the measured data is in good accordance with the Buckingham GS model.

    Combined with the physical and mechanical parameters, the correlation between the measured shear wave speed and the GS model is analyzed, and the results show that: The prediction trend of shear wave speed, porosity, mean particle size and GS model is consistent. The burial depth of seafloor sediments has great influence on shear wave speed, while the measurement frequency (1~5 kHz) has less influence on shear wave speed.

    In this paper, the in-situ low-medium frequency (300 Hz~34 kHz) sound speed of Jiaozhouwan seafloor sediment samples and the laboratory medium-high frequency （25~250 kHz）sound speed are measured. The shear wave speed (1~5 kHz) measurement of the Yellow Sea seafloor columnar sediment samples is carried out. This paper analyzes the relativity between sound speed and physical properties of fine-grained sediments. and expounds the dependence of the sound wave speed and the frequency on the basis of the sound propagation theory. The study has some reference significance to enrich the acoustic theory of seafloor and to promote the deep research of low-frequency acoustic characteristics and dispersion characteristics in seafloor sediments.

目录

摘 要... I

Abstract III

第1章 绪论... 1

1.1 选题背景及研究意义... 1

1.2 国内外研究现状... 3

1.2.1 海底沉积物声学特性研究现状与发展动态... 3

1.2.2 海底沉积物剪切波声学特性研究现状... 5

1.2.3 海底沉积物声波频散特性研究现状与发展动态... 6

1.2.4 声传播理论研究现状... 9

1.3 存在的问题... 10

1.4 本文的主要内容及创新点... 10

1.5 论文工作量统计... 11

第2章 实验设备... 12

2.1 中低频大尺度现场声学测量系统... 12

2.2.1 室内控制单元... 12

2.1.2 声学发射单元... 13

2.1.3 声学接收单元... 15

2.1.4 多通道自容式数据采集系统... 17

2.1.5 单通道自容式数据采集系统... 18

2.1.6 实时监控单元... 18

2.2 中高频实验室声学测量系统... 19

2.3 实验室剪切波柱状样品测量系统... 21

第3章 野外实验及数据处理... 24

3.1 野外实验... 24

3.1.1 系统技术路线及工作流程... 24

3.1.2 声源与接收阵列的布设... 26

3.1.3 探杆间距精确测量... 26

3.2 声波实验数据处理... 27

3.2.1 胶州湾低频声信号数据提取... 27

3.2.2 物理性质测试... 30

3.2.3 声学性质... 32

3.3 剪切波实验数据处理... 33

3.3.1 物理性质测试... 33

3.3.2 声学性质测试... 34

第4章 海洋沉积物声传播模型研究... 36

4.1 流体理论... 36

4.2 弹性理论... 37

4.2.1 Gassmann方程... 37

4.2.2 Buckingham理论... 38

4.3 多孔介质弹性理论... 39

4.3.1 Biot模型... 39

4.3.2 EDFM模型... 40

4.4 本文模型输入参数取值... 40

4.4.1 Biot模型输入参数取值... 40

4.4.2 GS模型输入参数取值... 41

第5章 沉积物声学性质与物理性质相关关系... 45

5.1 沉积物中低频声速与物理性质相关关系... 45

5.1.1 不同频率声速与密度相关关系... 45

5.1.2 不同频率声速与孔隙度相关关系... 46

5.1.3 不同频率声速与平均粒径相关关系... 47

5.1.4 不同频率声速与含水量相关关系... 49

5.2 剪切波声学参数与物理性质相关关系... 50

5.2.1 黄海海底沉积物纵横波速比与沉积物类型的相关性... 50

5.2.2 黄海沉积物剪切波速度与孔隙度相关性... 52

5.2.3 黄海沉积物剪切波速度与平均粒径相关关系... 53

第6章 频散特征分析... 56

6.1 实测声速与频率的相关性... 56

6.1.1 中低频声速与频率相关关系及拟合曲线... 57

6.1.2 所有频率声速与频率相关关系及拟合曲线... 59

6.1.3 声速与频率相关关系与预测模型对比... 63

6.2 实测剪切波速度与频率的相关性... 66

第7章 结论... 68

参考文献... 69

致谢... 74

作者简历及攻读学位期间发表的学术论文与研究成果... 75