Simulation study on oblique in situ acoustic longitudinal wave measurement of seafloor inhomogeneous sedimentary layer

doi:10.3969/j.issn.1001-909X.2023.04.006

Abstract

Abstract:

Acoustic characteristics of seafloor sediments are the basic elements of marine sound field calculation and engineering geological evaluation. In situ measurement is an effective means to accurately obtain acoustic characteristic parameters. The structure stratification characteristics and the existence of geological anomalies such as boulders lead to vertical and lateral heterogeneity, and the existing acoustic in situ measurement system is difficult to detect and recognize the nonuniform features, and there is a lack of discrimination reference for the identification of stratigraphic non-uniformity. In this study, an oblique acoustic in situ longitudinal wave measurement method based on the heterogeneity of seafloor deposition was proposed, and a simulation study on the oblique acoustic in situ measurement of sediments within a hundred meters was carried out by using the finite element method. According to the data of regional geological engineering exploration data in the East China Sea, three models of uniform sedimentary layer, stratified sedimentary layer, and a sedimentary layer containing the boulder were constructed, and a simulation of acoustic velocity measurement in the sedimentary layer was carried out based on oblique in situ measurement method. The results show that the oblique in situ measurement method was effective in identifying the inhomogeneity in the large-depth sedimentary layer. By introducing the concept of equivalent offset, the original acoustic velocity calculation formula was improved, effectively improving anomaly identification accuracy. The oblique acoustic in situ measurement method proposed in this study was an effective extension of the existing in situ measurement methods of sedimentary layers, which will help to promote the further application of in situ measurement in marine engineering surveys.

Key words: seafloor sedimentary layers, oblique acoustic in situ measurement, acoustic characteristic, simulation

CLC Number:

P733.23

WANG Ying, TAO Chunhui, ZHANG Guoyin, ZHOU Jianping, SHEN Honglei. Simulation study on oblique in situ acoustic longitudinal wave measurement of seafloor inhomogeneous sedimentary layer[J]. Journal of Marine Sciences, 2023, 41(4): 57-69.

Figures/Tables 14

Fig.1 Schematic diagram of four in situ measurement methods (Figure was modified from reference[4].)

Fig.2 Oblique acoustic in situ longitudinal wave measurement system and schematic diagram of working principle

Tab.1 Model basic parameter table

沉积类型	声速/(m·s^-1)	密度/ (kg·m^-3)	阻抗/(Pa·s·m^-1)
沉积物Ⅰ	1 500	1 600
沉积物Ⅱ	1 700	1 800
孤石	3 200	2 600	8.32×10⁶

Fig.3 Right perfect match layer transversal sound pressure

Fig.4 Acoustic propagation in homogeneous sediments model

Fig.5 Receiver pressure directly below the acoustic source change with time in the homogeneous sediment model

Fig.6 Model structure (a) and mapping grid subdivision (b) of stratified sedimentary layer model

Fig.7 Acoustic propagation in stratified sedimentary layer model

Fig.8 Model structure (a) and free grid division (b) of a sedimentary layer model containing the boulder

Fig.9 Receiver sound pressure in a model of a sedimentary layer containing the boulder

Fig.10 Acoustic propagation in a sedimentary layer modle containing the boulder

Fig.11 Sound velocity profiles of different models at different horizontal offsets

Fig.12 Acoustic velocity profiles of different models at different measuring point spacing

Fig.13 Optimized acoustic velocity profiles of different models at different measuring point spacing

References 25

[1]	陶春辉. 海底沉积物声学原位测试和特性研究[D]. 杭州: 浙江大学, 2005.
	TAO C H. In situ acoustic experiment and properties study in marine sediments[D]. Hangzhou: Zhejiang University, 2005.
[2]	潘国富. 南海北部海底浅部沉积物声学特性研究[D]. 上海: 同济大学, 2003.
	PAN G F. Research on the acoustic characteristics of seabed sediments in the northern South China Sea[D]. Shanghai: Tongji University, 2003.
[3]	孟祥龙. CT探测技术在跨海顶管孤石群探测的应用研究[J]. 铁道建筑技术, 2021(1):150-154.
	MENG X L. Application research of CT detection technology in boulder group detection of cross-sea pipe jacking[J]. Railway Construction Technology, 2021(1): 150-154.
[4]	刘保华, 阚光明, 李官保. 海底沉积物声学特性测量技术与应用[M]. 北京: 科学出版社, 2019:38-50.
	LIU B H, KAN G M, LI G B. Seafloor sediment acoustic measurement techniques and applications[M]. Beijing: Science Press, 2019: 38-50.
[5]	王景强, 李官保, 阚光明, 等. 深海海底沉积物声学特性原位测量试验研究[J]. 地球物理学报, 2020, 63(12):4463-4472. DOI
	WANG J Q, LI G B, KAN G M, et al. Experiment study of the in situ acoustic measurement in seafloor sediments from deep sea[J]. Chinese Journal of Geophysics, 2020, 63(12): 4463-4472.
[6]	陶春辉, 金肖兵, 金翔龙, 等. 多频海底声学原位测试系统研制和试用[J]. 海洋学报:中文版, 2006, 28(2):46-50.
	TAO C H, JIN X B, JIN X L, et al. Development of multi-frequency in situ marine sediment geoacoustic measuring system[J]. Acta Oceanologica Sinica, 2006, 28(2): 46-50.
[7]	BARBAGELATA A, RICHARDSON M, MIASCHI B, et al. ISSAMS: An in situ sediment acoustic measurement system[C]// Shear waves in marine sediments. Dordrecht: Springer Netherlands, 1991: 305-312.
[8]	KRAFT B J, MAYER L A, SIMPKIN P, et al. Calculation of in situ acoustic wave properties in marine sediments[C]// Impact of littoral environmental variability of acoustic predictions and sonar performance. Dordrecht: Springer Netherlands, 2002: 123-130.
[9]	LEE K M, BALLARD M S, MCNEESE A R, et al. In situ measurements of sediment acoustic properties in Currituck Sound and comparison to models[J]. The Journal of the Acoustical Society of America, 2016, 140(5): 3593-3606. DOI URL
[10]	HEFNER B T, JACKSON D R, WILLIAMS K L, et al. Mid- to high-frequency acoustic penetration and propagation measurements in a sandy sediment[J]. IEEE Journal of Oceanic Engineering, 2009, 34(4): 372-387. DOI URL
[11]	ROBB G B N, BEST A I, DIX J K, et al. Measurement of the in situ compressional wave properties of marine sediments[J]. IEEE Journal of Oceanic Engineering, 2007, 32(2): 484-496. DOI URL
[12]	BEST A I, ROBERTS J A, SOMERS M L. A new instrument for making in-situ acoustic and geotechnical measurements in seafloor sediments[J]. Underwater Technology, 1998, 23(3): 123-131. DOI URL
[13]	阚光明, 刘保华, 韩国忠, 等. 原位测量技术在黄海沉积声学调查中的应用[J]. 海洋学报, 2010, 32(3):88-94.
	KAN G M, LIU B H, HAN G Z, et al. Application of in-situ measurement technology to the survey of seafloor sediment acoustic properties in the Huanghai Sea[J]. Acta Oceanologica Sinica, 2010, 32(3): 88-94. DOI URL
[14]	WANG J Q, LI G B, LIU B H, et al. Experimental study of the ballast in situ sediment acoustic measurement system in South China Sea[J]. Marine Georesources & Geotechnology, 2018, 36(5): 515-521.
[15]	FU S S, WILKENS R H, FRAZER L N. Acoustic lance: New in situ seafloor velocity profiles[J]. The Journal of the Acoustical Society of America, 1996, 99(1): 234-242. DOI URL
[16]	TAO C H, DENG X M, LI H X, et al. Development of in situ marine sediment geo-acoustic measurement system with real-time and multi frequencies (the second generation)[J]. China Ocean Engineering, 2009, 23(4): 769-778.
[17]	YANG J, TANG D J, WILLIAMS K L. Direct measurement of sediment sound speed in Shallow Water’06[J]. The Journal of the Acoustical Society of America, 2008, 124(3): EL116-EL121. DOI URL
[18]	刘伯胜, 黄益旺, 陈文剑, 等. 水声学原理[M].第三版. 北京: 科学出版社, 2020:65-83.
	LIU B S, HUANG Y W, CHEN W J, et al. Principles of underwater acoustics[M]. 3rd ed. Beijing: Science Press, 2020: 65-83.
[19]	周志远, 高金耀, 吴招才, 等. 东海莫霍面起伏与地壳减薄特征初步分析[J]. 海洋学研究, 2013, 31(1):16-25.
	ZHOU Z Y, GAO J Y, WU Z C, et al. Preliminary analyses of the characteristics of Moho undulation and crustal thinning in East China Sea[J]. Journal of Marine Sciences, 2013, 31(1): 16-25.
[20]	李红星. 杭州湾沉积物原位声学特性分析及浅表低速层研究[D]. 长春: 吉林大学, 2008.
	LI H X. In-situ acoustic properties analyse of the sediment in Hangzhou Bay and surface low-velocity layer study[D]. Changchun: Jilin University, 2008.
[21]	周建平, 吕文正, 陶春辉. 海底柱状沉积物超声测量[J]. 东海海洋, 2003, 21(4):26-33.
	ZHOU J P, LÜ W Z, TAO C H. Ultrasonic measurement of seafloor sediment cores[J]. Donghai Marine Science, 2003, 21(4): 26-33.
[22]	张慧. 花岗岩声波波速与岩体弹性模量的统计分析[J]. 低碳世界, 2016(2):110.
	ZHANG H. Statistical analysis of acoustic wave velocity and elastic modulus of granite[J]. Low Carbon World, 2016(2): 110.
[23]	YANG J, JACKSON D R. Measurement of sound speed in fine-grained sediments during the seabed characterization experiment[J]. IEEE Journal of Oceanic Engineering, 2020, 45(1): 39-50. DOI URL
[24]	ASTM STANDARDS. Standard test methods for downhole seismic testing: ASTM D7400-08[S]. PA: ASTM Interna-tional, 2008.
[25]	李倩宇, 陶春辉, 周建平, 等. 海底沉积物声学原位信号自动拾取方法研究[J]. 杭州电子科技大学学报:自然科学版, 2019, 39(2):18-21,39.
	LI Q Y, TAO C H, ZHOU J P, et al. Study of the in-situ acoustic signal automatic picking in seafloor sediment[J]. Journal of Hangzhou Dianzi University: Natural Sciences, 2019, 39(2): 18-21, 39.