共查询到20条相似文献，搜索用时 140 毫秒
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水下工程前期调查广泛采用各种地球物理的手段来解决工程问题,本文根据浅地层剖面仪探测资料,分析拟建栅栏式防波堤工程海底的地层状况,为栅栏式防波堤工程基础设计提供地层分布及持力层的依据。 相似文献
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在海上油田开发过程中,往往存在一些当时不具备开发条件的水下井口。这些井口一方面现阶段具有重新开发价值,另一方面也是海洋工程建设的障碍物。而水下井口尺度小,常用的调查手段较难探测到。文中介绍了浅地层剖面仪和磁力仪的原理,并开展了浅地层剖面仪和磁力仪综合探测水下井口的应用与分析。结果表明浅地层剖面仪和磁力仪均可探测到井口,在浅地层剖面图像上表现为垂向的声学空白带,为桩坑和井口的反射;磁异常平面等值线为等轴状,存在极大值和极小值,井口位于极大值和极小值之间。浅地层剖面仪和磁力仪探测的井口位置相差1 m,与给定井口坐标偏差2 m,满足工程需求。因此使用浅地层剖面仪和磁力仪综合探测水下井口在现阶段不失为一种可行的方法。 相似文献
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利用声学浅地层剖面仪对海底管道在海底的赋存状态检测是确保海底输油气管道安全运行的重要措施之一。介绍了新型参量阵浅地层剖面仪SES-2000的基本原理及其特点,通过对福建湄洲湾LNG海底管道检测实际应用,有效识别出了埋藏、裸露和悬空等3类海底管道赋存状态,尤其对沙包回填治理后的管道埋深能有效探测识别。检测结果表明,该设备具有高分辨率和强穿透的特点,稳定性好,能获取高品质的管道检测数据,应用效果良好。获取的基础数据为海底管道日常维护提供了科学依据和技术支持。 相似文献
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浅地层剖面探测技术及应用 总被引：1，自引：0，他引：1
浅地层剖面技术是应用声学原理高效获取海底面之下浅部地质地球物理信息的探测技术,主要应用于海底浅地层信息探测和海底特殊目标调查等方面。以往研究者主要集中在浅地层剖面的具体应用,未对不同类型的浅剖应用效果进行综合对比分析,本文比较4种不同类型浅地层剖面系统的组成、工作方式和探测技术参数,认为不同尺度的探测目标需要应用不同类型的浅地层剖面系统。分析和对比不同震源类型浅剖的应用案例,发现电火花震源穿透能力最强,分辨率随工作频率的增大而提高;电磁式震源穿透深度与分辨率适中;压电换能器震源分辨率较高,穿透能力弱;参量阵震源利用差频原理,信号中包含高频与低频两部分,能够同时得到较高的分辨率与较大的穿透深度。未来浅地层剖面探测技术向深穿透、高分辨率、高效率、二维向三维甚至高维探测方面发展。 相似文献
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随着我国海洋地质研究工作和水下工程的迅速发展,为了探测海底以下地层的分层结构,要求以高速声学探测仪器代替或减少钻井的数量。浅地层剖面仪就是利用回声测深的原理研制成的,它可以在测船航行时,连续、自动地在记录纸上直接描绘出海底以下地层的剖面图。 目前,国外已有近百种浅地层剖面仪,我国也先后研制出了多种类型的产品。我所研制出的HDP-1型浅地层剖面仪,经过多次海上工作的考验,提供了数千公里的地层剖面资 相似文献
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海底管道的位置与埋深测量通常采用浅地层剖面仪等声学手段来实现,由于海管与地层之间的声阻抗差异,会以绕射弧的形态出现在声学剖面中。但当海管埋设于管沟中时,管沟中断棱的绕射与海管绕射易于混淆,给声学剖面图的解译和识别带来困难。基于地震勘探原理,结合浅地层剖面仪的性能、挖沟作业对地层的扰动等,分析了管沟绕射弧的类型与特点、挖沟作业扰动的声学特征等,提出了管沟中海管绕射弧的识别方法。结果表明,正确认识不同类型管沟的绕射、施工扰动产生的绕射等声学特征,才能辨识出海管的绕射现象。实际工作中应根据测量海区的水深、土质、海管属性等多种要素,选用适宜的仪器类型及测量参数。 相似文献
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High-resolution Echo-sounding and Detection of Embedded Archaeological Objects with Nonlinear Sub-bottom Profilers 总被引：3，自引：0，他引：3
Sub-bottom profilers based on nonlinear acoustics offer many advantages especially for detecting and locating embedded objects
in shallow waters. They have a narrow beam in spite of small transducers and virtually no side lobes. It is possible to realize
mobile low-frequent sub-bottom profilers, which transmit very short sound pulses. Excellent vertical as well as horizontal
resolutions at reasonable penetrations are proven benefits of using this technique. In this paper some technical aspects are
discussed and a new experimental nonlinear scanning sub-bottom profiler system is described. Results from a field trial in
archaeological prospection are shown to illustrate the successful application in practice. 相似文献
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Reflection Coefficient Calculation from Marine High Resolution Seismic Reflection (Chirp) Data and Application to an Archaeological Case Study 总被引：2，自引：0，他引：2
Chirp sub-bottom profilers produce high-resolution images of the near-surface. An attribute of the sea-bed reflection in chirp data are fluctuations in polarity between adjacent traces. Two models are proposed and presented to explain this: the first incorporates changes in an acoustic impedance gradient at the sea bed; the second uses changes in the thickness of the uppermost sediment layer. Mixing of adjacent traces produces a consistent polarity for the sea-bed reflector. Reflection coefficients are calculated, using amplitude information derived from single-traces, and polarity information from trace mixing, with application to a marine archaeological case study. The reflection coefficient calculated for the top of a buried 18th century wooden wreck is -0.26. 相似文献
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Pinto M.A. Bellettini A. Hollett R. Tesei A. 《Oceanic Engineering, IEEE Journal of》2002,27(3):484-494
Results from two field experiments aimed at investigating the detection and classification of buried targets are presented. In both experiments a 2-16-kHz parametric source was used. In the first experiment, the source was used in combination with a 12-m horizontal line array and in the second with a 1.4-m vertical line array which was displaced horizontally along an underwater rail to form a 10 m /spl times/ 1.4 m two-dimensional synthetic aperture sonar (SAS). To increase the SAS integration time, the parametric source was electronically scanned in azimuth during the displacement along the rail, as in spotlight mode. It is shown that both arrays allow important signal-to-reverberation gains, enhancing the detection of sub-bottom echoes. A new, environmentally adaptive, matched filter which further improves the signal to reverberation ratio while allowing discrimination between proud and buried targets is presented and validated experimentally. The use of resonant scattering for target classification of buried objects is discussed, in the particular case of spherical shells. 相似文献
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近海海上风电场水下噪声传播模型适用性研究 总被引：1，自引：0，他引：1
通过现场采集近海海上风电场工程区运营期风机水下噪声和背景噪声数据,计算了噪声信号的倍频带声压级,功率谱级和峰值声压级,确定了海上风电场水下噪声总声源级为148.3 d B,以此开展近海海上风电工程风机水下噪声频域特性、功率密度谱特性等研究。在此基础上使用Kraken简正波模型和Bellhop射线模型对风电场运营期风机水下噪声在水平与垂直方向上的传播进行模拟,模拟了噪声在不同频带内的衰减程度,结果显示模型模拟结果在不同频率下的衰减趋势有着很大差异,产生了明显的多途干涉现象,通过实测数据对建立的噪声传播模型进行验证,发现Kraken简正波模型在500 Hz以下,Bellhop射线模型在500 Hz以上适合模拟实际水下噪声传播情形,同时海区本身背景噪声的存在会对预测的准确性产生影响。这些结论可用于进一步对近海海上风电场水下噪声传播的研究。 相似文献
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Underwater topography detection of Shuangzi Reefs with SAR images acquired in different time 总被引：3，自引：1，他引：3
1 IntroductionSynthetic aperture radar (SAR) is one of theadvanced microwave remote sensors of environmentand resource. It can observe targets in all weathersand all day and night in a multi-band, multi-polari-zation and multi-look angle mode. SAR has bee… 相似文献
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水声宽带信号波形预报技术研究 总被引：1，自引：0，他引：1
为了实现远程水下目标微弱信号检测,掌握远程传输后信号波形的特征,水声宽带信号波形预报技术是研究水下信号精细化特征研究的重要突破口之一.针对宽带信号,采用波束位移射线简正波(BDRM)频域合成波形预报算法和 BELLHOP 射线时域波形预报算法,获得宽带信号远程波形预报模型,并在浅海负跃层和深海声道两种典型海洋环境下,利用上述两种宽带波形预报算法,仿真计算了宽带信号远程波形,比较了两种波形预报算法精度.结果表明,在一定条件下,两种模型具有同等计算精度,可满足不同条件下的信号波形预报需求. 相似文献
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Gutowski Martin Bull Jon Henstock Tim Dix Justin Hogarth Peter Leighton Tim White Paul 《Marine Geophysical Researches》2002,23(5-6):481-492
Chirp sub-bottom profilers are marine sonar systems which use a highly repeatable source signature to facilitate the acquisition of correlated data with decimetre vertical resolution in the top 20–30 m of sediments. Source signatures can be readily developed and implemented, but an applicable methodology for assessing resolution and attenuation characteristics of these wide-band systems did not exist. Methodologies are developed and applied to seven contrasting source signatures which occupy the same frequency band, but differ in their Envelope and Instantaneous Frequency functions. For the Chirp source signatures tested, a Sine-Squared envelope function is shown to produce seismic data with the optimum resolution and penetration characteristics. 相似文献
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The results of a laboratory experimental program aimed at better understanding the scour around and burial of heavy cylindrical objects under oscillating flow on a sandy bed are described. This study was motivated by its application to the dynamics of isolated cobbles/mines on a sandy floor under nonlinear progressive waves, such as that occur in shallow coastal waters beyond the wave-breaking region. In the experiments, nonlinear progressive waves were generated in a long wave tank of rectangular cross-section with a bottom slope. Model mines (short cylinders) were placed on the sandy bottom and the temporal evolution of the bed profile and the velocity field in the near field of the object were observed. Experiments were conducted at relatively high Reynolds numbers for a range of flow conditions, which can be characterized by the Keulegan–Carpenter number and Shields parameter. Depending on the values of these parameters, four different scour regimes around the cylinder including periodical burial of cylinder under migrating sand ripples were observed; they were classified as: (i) no scour/burial, (ii) initial scour, (iii) expanded scour, and (iv) periodic burial cases. A scour regime diagram was developed and the demarcation criteria between different regimes were deduced. Semi-empirical formulae that permit estimation of the scour depth with time, the equilibrium maximum scour depth and length, and conditions necessary for the burial of the cylinder as a function of main external parameters are also proposed. 相似文献
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A remote sediment classification technique based on attenuation measurements from Chirp sub-bottom profiler data is described. This differs from previously published work in that attenuation measurements are obtained for each stratigraphic unit within a complex, thinly interbedded sedimentary sequence. Compressional wave attenuation measurements are obtained for a wide variety of lithologies, including muds, silts, sands, clayey sands, silty clays and gravel lags, with grain sizes ranging from 8 Phi to -4 Phi. In addition, attenuation measurements from sub-bottom profiler data were calibrated against laboratory acoustic measurements of vibracores and seabed samples from corresponding geographic locations, under simulated in-situ conditions using a Pulse Tube method. We adapt an instantaneous frequency matching method using a causal attenuation filter to model the decay of the Chirp transmitted waveform. From this modelling, a relationship between t* (a causal attenuation operator) and change in instantaneous frequency is established. The Hilbert transform is used to extract instantaneous frequency information from Chirp seismic, which is used to derive attenuation information for selected individual stratigraphic layers imaged by the sub-bottom profiler. This paper draws attention to the limitations in comparing attenuation measurements derived from Chirp sub-bottom profiler data against previously published literature on experimental attenuation measurements, which are limited by the wide variance of these data, and the difficulty in finding a meaningful best fit to these data. This demonstrates the importance of calibrating remote sediment classification observations using complimentary acoustic analysis of seabed samples to generate a site-specific geoacoustic database. A positive correlation between laboratory and sub-bottom profiler attenuation measurements was obtained, with a correlation coefficient of 0.885. Poorly sorted gravels with a mixed lithic and biogenic pebble component are characterised by very high attenuation with values of Q from 4 to 19. These sediments are considerably coarser-grained than those typically described in previously published experimental studies. 相似文献