共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
3.
Lei Sun Xiangmei Meng Guanbao Li Guangming Kan Baohua Liu 《Marine Georesources & Geotechnology》2020,38(5):595-603
AbstractThe high-frequency acoustic properties of seafloor sediments are very significant in seafloor study and underwater acoustic study field. In order to measure the sound speed and the attenuation for the small-scale sediment cores more accurately, this study developed a water coupled acoustic laboratory measurement system based on Richardson-Briggs technique. This method used the correlation comparison of waveforms received in sediment core and in identical reference tubes filled with water to measure sound speed and attenuation. The sound speed and attenuation of a clayey silt sediment sample were measured using the water coupled acoustic laboratory measurement system. This frequency dependence of the sound speed and attenuation showed that the clayey silt sediment has a weak positive sound speed dispersion, while the attenuation increases with a strong positive gradient within the measurement frequency range. This study also noted that the measured sound speed ratio match well with the empirical equations from literature. The measured attenuation factor data can fall in the Hamilton’s empirical prediction range. 相似文献
4.
Bin Lv Guo-liang Qi Guan-bao Li Guang-ming Kan Jing-qiang Wang Jie Liu 《Marine Georesources & Geotechnology》2020,38(3):363-373
AbstractA new kind of visual acoustic measurement system was developed to obtain the acoustic characteristics of seabed sediment and the working state of in situ measuring equipment in real time. The control unit of the system structure is mainly made up of the underwater control unit and the deck control unit. In comparison with similar traditional systems, the system can transmit the working video image, the measured acoustic data and the waveform synchronous from the underwater control equipment to the deck control unit through the connecting cable. Apart from self-contained in situ measurement, the working modes of it include visual online real-time control. In order to guarantee the stability and measurement precision of the video control system, the process control of in situ measurement was strictly tested in the experimental tank. In 2017, sea trials of the in situ measurement system was carried out in the South China Sea. In the process, data related to measurement, including the acoustic velocity and attenuation coefficient of the seabed sediment, were obtained as well. The results from sea trials show that the control process of the visual system is intuitive, reliable and accurate, and therefore it can be popularized and applied. 相似文献
5.
This paper describes a system that has been developed to measure compressional wave speed in cored marine sediments onboard ship. The structure enables one to secure an extruded core sample to its base and to move acoustic probes to a desired location, implant them to a specified depth into the sample and perform the measurement. The acoustic measurement system is a pulse-time delay system measuring time difference over a fixed path length and the temperature of the sediment. The time difference and temperature measurement systems are comprised of task oriented components and are housed in a single portable box. The system is adaptable to the various sample sizes obtained with the coring apparatus presently in use. Initial field tests indicate that ship motion has no effect on the system. Data collected from cores has been classified according to sediment type and displays good agreement with data presented by Hamilton (1970). The difference in compressional wave velocity, based on sediment type, for the two studies is 5 m per sec. 相似文献
6.
南沙海域深水区表层沉积物声速与孔隙度相关关系 总被引：5，自引：0，他引：5
采用同轴差距测量法对南沙海域海底沉积物取样进行甲板现场声学测量,并计算了声速,结合沉积物取样分析获得的孔隙度,研究了海底表层100 cm沉积物的声速和孔隙度之间的相互关系,分析获得了孔隙度与海底沉积物声速关系的经验公式,结果表明此海域沉积物声速的临界孔隙度为67.80%。将此公式与国内外其他学者建立的经验公式进行了对比,分析发现各预测方程之间存在着差异,说明不同海域的沉积物声学特性具有差异性,经验公式具有区域性,同时分析了其他影响声速的因素。此项工作对于建立和研究南海声场环境具有重要意义。 相似文献
7.
Tao Liu San-Peng Li Hai-lei Kou Wan-li Chai Guan-li Wei 《Marine Georesources & Geotechnology》2013,31(7):775-782
AbstractFiber Bragg Grating (FBG) technology has emerged as a relatively new sensing technology for engineering applications because of lots of advantages. In this study, a large diameter probe instrumented with FBG pressure sensors to monitor excess pore pressure in marine sediment is proposed. The principle of FBG differential pressure sensor was introduced. Laboratory tests were carried out to check the workability and stability of the FBG pressure sensor. Offshore field test was also conducted in a wharf in Qingdao of China to evaluate the feasibility of the proposed probe. The installation procedure of the probe was introduced in detail. The excess pore pressure in dissipation test, after installation and pulling process were reported. The permeability coefficient of marine sediment was calculated based on the measured data. The field data show that the proposed probe based on FBG pressure sensor has good feasibility and accuracy in monitoring the excess pore pressure of marine sediment. The generation and dissipation of excess pore pressure is closely related to the degree of soil disturbance. The variation of excess pore pressure after installation can reflect the tide well in the site. 相似文献
8.
Laboratory equipment has been built which will measure the permeability and thermal conductivity of deep-sea sediments at their in-situ conditions of hydrostatic pressure, temperature, and void ratio. The apparatus has the capability of uniaxially consolidating a sediment sample to simulate compaction within the sediment column, while exposing the specimen to hydrostatic pressures ranging from atmospheric to 62 MPa and to temperatures from 22 to 220°C. The equipment includes a hypodermic needle mounted vertically through the base of the pressure vessel from which thermal conductivity is determined by the needle probe method. The system also features a combination of dead-weight testers which produces a small hydraulic gradient across the sample and permits the measurement of sediment permeability at large hydrostatic pressures.The physical property data generated from this apparatus will be important in understanding the mechanisms of heat transfer through the ocean floor and in analysing the coupled flow of heat and pore fluid in the vicinity of a heat source, such as a radioactive waste canister, buried in the seabed. 相似文献
9.
本文针对温度差异对沉积物的声学特性的影响,研究不同温度下沉积物的频谱特征规律。把南海深海沉积物的人工样品置于温控环境中,采集经历沉积物的超声信号,对其进行快速傅里叶变换获得频谱特征,分别从主频漂移、主频幅值、主频频宽、接收能量等方面归纳出温度影响下的海底沉积物超声信号的频谱特征规律：如温度变化影响频谱特征,但可重复性低;温度增加使沉积物对声信号的衰减增大;频宽与频率幅值呈负相关,但温度-幅值的关系明显于温度-频宽的关系。因此,温度改变导致沉积物超声信号频谱的规律性变化。 相似文献
10.
Michael Tubman 《Marine Georesources & Geotechnology》2013,31(1-4):123-134
Abstract From September 1975 to April 1976 offshore production Platform V in South Pass, Block 28 (East Bay, Louisiana), was instrumented to measure the effect of storm waves on the soft sediments typical of the Mississippi delta (in a project given the acronym SEASWAB). A portion of this project consisted of four identifiable units of instrumentation (see note): (1) an accelerometer package buried 1 m in the sediment to measure three‐dimensional sediment accelerations and an associated pressure transducer, which measured wave‐induced pressures; (2) an array of instruments that included a wave staff, electromagnetic current meter, and a pressure transducer to examine various relationships between wave properties; (3) a wave‐, current‐, and wind‐measuring station 3.35 km inshore of Platform V to determine the transformation of the waves as they moved over the sediments; and (4) a transponder buried in the mud, the position monitored so that long‐term mudflow could be measured. The direct measurement of seafloor oscillations required the unique instrumentation of the accelerometer system. Three Bruel and Kjaer 8306 accelerometers mounted at right angles to each other made possible the measurement of small oscillations (～0.01 m) at low frequencies (0.1–0.3 Hz). The acoustic method of measuring long‐term mudflow was subject to problems associated with sound propagation in shallow water. The range of the system was found to be 2.74 km, apparently independent of depth. Multiple returns received after single interrogations of the transponder decreased the accuracy of the system. 相似文献
11.
Louis E. Garrison 《Marine Georesources & Geotechnology》2013,31(1-4):117-122
Abstract SEASWAB is one element of the Delta Project of the U.S. Geological Survey, a cooperative effort with several universities and other governmental agencies to investigate the processes that cause marine‐sediment instability. The basic purpose of the SEASWAB experiment was to obtain field measurements of sediment motion and pore‐pressure variations in soft sediment affected by wave‐pressure perturbations. This article serves as an introduction to the six papers that follow and that together make up a report on the results of SEASWAB. 相似文献
12.
Near-bottom normal incidence acoustic reflection data and sediment physical property data are used to study the relationships between acoustic reflections and sediment physical properties. A pinger-hydrophone experiment was performed to obtain the necessary acoustic reflection data. In addition, a standard piston core was retrieved in the acoustic survey area for physical property analysis. The piston core was sampled and 13 properties were measured at 55 locations within the top 12 m of the core. Correlation studies amongst the sediment physical properties resulted in the following strong correlations: acoustic impedance () and porosity (), (0.96); water content () and , (0.95); bulk density () and , (0.99).The empirical orthonormal function (EOF) method was employed for acoustic signal analysis. This method assumes no a-priori models of the sediment or causality. The EOF method reduced the acoustic data to 8 functions that contained 97.6% of the sample variance. The EOFs were subsequently analysed by using cepstrum analysis which reveals time delay information and enhances detecting zones of reflectivity. The result of the sediment physical property and cepstrum analysis indicates that zones of reflectivity are essentially zones of relatively high acoustic impedance, low porosity, and low phi (high mean grain size). 相似文献
13.
Acoustic environment and physico‐mechanical properties of the shelf seabed off the pearl river mouth
Abstract The vast shallow sea off the Pearl River mouth in the northern South China Sea is an important prospecting area for offshore oil development. In recent years, the authors have investigated acoustic and geotechnical characteristics of marine sediments in this area. An intercalated layer of low sound velocity and low compressive strength has been found within the seabed, in which the median diameter of sediment grains is fine and the sound velocity is 100–200 m/s lower than that of the overlying and underlying layers. The minimum unconfined compressive strength of this layer is 0.075 kg/cm2, which is lower than that of the over‐ and underlying layers by an order of magnitude. Such an intercalation often constitutes a threat to the stability of shallow foundation soil. In case of overloading, the layer may be weakened, and seafloor sliding between different sediment layers may occur. The regional distribution of these kinds of weak intercalations of low sound velocity may be traced by a subbottom profiler and by means of sediment acoustical investigations. Correlation between the gray level of a layer on subbottom profile records and physical properties of the layer (including sound velocity and reflectivity) suggests that the layer of sufficient bearing capacity must be searched by means of sediment acoustics at least to the depth of a high‐velocity substratum of stronger reflection. 相似文献
14.
水体悬沙浓度是水利、环境、河口海岸与海洋相关研究领域最为基础的数据需求之一。随着传感器技术的发展, 悬沙浓度连续测量技术在悬沙浓度测量领域表现出高时空分辨率、长期数据采集的成本和风险均较低的突出优点。本文综述了光学、声学、音叉谐振、压差和放射性射线衰减等原理用于悬沙浓度连续测量技术的相关研究进展, 探讨了各技术方法的优、缺点, 并提出了今后的研发重点和发展方向主要在以下几个方面: 1) 光后向散射原理是低成本、小型化和高时频测量悬沙浓度的最优技术路线, 需着力于开展量程扩增和粒径敏感度削弱研究; 2) 低不确定度悬沙浓度垂向剖面观测的实现依赖于超声后向散射原理技术路线的发展; 3) 音叉谐振原理技术路线尤为契合高含沙水流和浮泥工况下的超高量程应用场景; 4) 多技术路线传感器融合以及使用人工智能算法模型替代正向反演模型。 相似文献
15.
16.
海底沉积物的声学声速特性是沉积物声学中的一个重要的研究方向。正确提取声学原位测量的声速对海底沉积物声学反演至关重要。分析了海底声学原位测试系统的输出子波特性,提出了基于子波提取的互相关双向极值声速提取法。在声速提取过程中,发现某些通道实测声波到达时会出现超出正常范围的异常。分析后认为异常通道的到达波相位出现180°反至现象。通过互相关数值的负极小值提取的声波到达时对互相关正极大值所获得的到达时曲线进行校正后提取声速,得到了正确的结果,说明了本方法的正确性。 相似文献
17.
Pore pressures in marine sediments: An overview of measurement techniques and some geological and engineering applications 总被引：1，自引：0，他引：1
P. J. Schultheiss 《Marine Geophysical Researches》1990,12(1-2):153-168
Pore pressures in the seabed are extremely sensitive to any imposed stress because of the low permeabilities commonly exhibited by marine sediments. Consequently, the measurement of sediment pore pressures can be used to infer either the nature of the imposed stress (if the sediment properties are known) or the physical properties of the sediment (if the imposed stresses are known). Stresses of many different types may be exerted on the seabed either through hydrostatic forces (e.g. tidal and wave effects), or directly by lithospheric forces (e.g. tectonic and thermal forces). Several techniques for measuring in situ pore pressures in the upper few metres of sediments have been developed, and one instrument, the PUPPI, will operate autonomously in water depths up to 6000 m. Basic sediment properties and processes can already be inferred from pore pressure responses using this technique. However, further application and development could greatly enhance its capability, especially for long-term monitoring of sediment conditions. In this Chapter, pore pressure measurement techniques are briefly reviewed and problems are highlighted. An outline is given of some of the many ways in which pore pressure measurements could be used to gain further insight into geological processes and to determine some of the pertinent sediment properties more accurately for engineering applications. 相似文献
18.
Ostrovskii A. G. Zatsepin A. G. Shvoev D. A. Volkov S. V. Kochetov O. Yu. Olshanskiy V. M. 《Oceanology》2020,60(6):861-868
The article is devoted to the development of an autonomous profiling system for measuring the aquatic environment under ice. The system moves up and down in the water column along a cable with a load at the lower end, which is lowered into a lane in the ice. The system carrier is designed for transporting an acoustic Doppler current profiler and a salinity, temperature, and pressure probe. The system will be useful for long-term measurements of vertical profiles of the current speed and marine environment parameters, as well as ice draft. The article describes in detail the structure and operation of the system. The hydraulic scheme of the carrier buoyancy system is presented.
相似文献19.
C. C. Liao 《Marine Georesources & Geotechnology》2013,31(9):1149-1150
AbstractThe excess pore pressure accumulation is a key factor when estimating the formation mechanism of large pockmarks, as it determines the liquefaction potential of marine sediments due to water waves. The governing equations for excess pore pressure may have different forms for various types of sediments and then shall reflect the cyclic plasticity of the soil. For water waves propagating over a porous seabed, the liquefaction area induced by waves is generally progressive, which indicates that the liquefaction area will move forward following the wave train. Therefore, the excess pore pressure accumulation can be used to explain the occurrence of the large pockmarks, but the dimension of the pockmark may be related to the heterogeneity of sediment or the wave properties affected by the topography in the subaqueous Yellow River Delta. 相似文献