海水和沉积物中声传播损失的仿真分析

文章建立了水—沉积物—海底半空间的分层海底模型,通过仿真计算,比较了声波在海水和沉积物中接收时的传播损失差异。结果表明,在高声速海底的条件下,声波在沉积物中传播且频率较低时,传播损失较低,即低频声波更易于在沉积物中传播。     

常见潜在灾害性地质条件及其对海上施工的影响

根据海洋工程地质勘察的实践和资料解释方面的经验,对海底冲刷、浅层气、断层和古河道等潜在的灾害性工程地质现象的勘察,以及工程地质条件评价做简要的特征描述.地质勘察和工程地质评价,对认识古地层环境、工程地质特性、海上施工、海上建筑以及防灾减灾具有重要意义.     

新型海底沉积物采样器结构设计及采样过程仿真分析

针对海底沉积物采集的特点,设计了新型海底沉积物采样器,将采样和保真融为一体,利用海底触发装置实现采样,利用海水等静压原理实现采样器的封口与保真,采用FLUENT软件对采样过程进行了模拟仿真,并对采样的动态过程进行了分析,结果显示在下落高度足够时,采样器撞击海底的速度趋于稳定值,同时攻角小于5°时采样时所受的阻力最小.     

基于耦合理论的海底地震仪设计方法研究

进行航行舰船地震波观测时,必须考虑海底地震仪(OBS)与海底的耦合问题.由于大部分海底被一层厚厚的松软沉积物覆盖,所以海底地震仪响应会严重影响海底表面的运动.并且海底地震仪位于流体与固体的边界上,浮力的作用也会影响质点运动.对于不同类型的地震波,作用力与质点运动并不满足我们所期望的关系.本文介绍了海底地震仪与沉积物的耦合模型,将其简化为质量 - 弹簧 - 阻尼器系统.响应特性主要取决于OBS的质量、结构、刚性以及沉积物密度.通过理论计算,得到影响海底耦合的主要因素,并在此基础上提出海底数字地震仪的合理设计方法.     

复杂地质条件下海底管道路由选择技术

海底管道是海洋油气田开发的重要组成部分,随着我国海洋油气田的大规模开采,海底管道在未来海洋石油工业链条中的纽带作用将越加突出。首先介绍海底管道路由选择面临的海床地质特征:海床不平整、冲刷、断层、液化等,其次介绍基于复杂地质条件海底管道路由选择流程和接受标准,最终阐述海底管道路由选择的设计方法。本文的研究成果既是对中国海区已运行项目的总结,也为我国南海深水油气田开发及拓展国外市场提供参考。     

北冰洋结冰期可追溯到4千万年前

日本九州大学海洋地质学和古环境学教授高桥孝三，发表了国际综合大洋钻探计划(IO)DP)在北冰洋实施的调查结果。高桥教授称，此次使用挪威的钻探船在北冰洋极点附近、水深约1200米的4处海底，成功地采集到海底地层428米的沉积物样品。根据这些海底地层沉积物样品分析，发现海底地下约300米的地层中，     

海底三维散射模型仿真研究

海底声散射强度是浅海混响预报的一个重要物理量.采用Jackson复合粗糙度模型研究了非均匀海底界面的声散射问题,对模型进行了理论推导和仿真计算,利用已发表的海底散射强度实测数据与模型仿真结果进行对照,验证了模型的正确性,并就海底沉积物类型和海底声学特性参数对海底反向散射强度的影响进行了分析.     

海底地震仪的优化设计

海底地震仪可用于探测航行舰船地震波信号。然而,由于信噪比较低,容易造成试验数据的失真。主要原因是海底地震仪（OBS）与海底表面的耦合较差。本文根据现有的OBS与沉积物耦合理论,总结了OBS的设计方法：①最小化质量;②合理的与沉积物接触部分的半径;③OBS接近于周围介质的密度;④最小化水中OBS的剖面以及横切面;⑤低密度梯度及关于垂直轴的最大对称性。结合理论,对现役的海底地震仪进行了结构分析。     

陆丰7-2海底管道铺设敏感性分析

海底管道铺设过程的敏感性分析是海底管道安装设计的重要内容,通过海底管道铺设敏感性分析可以明确铺管作业的操作参数,为海上铺管作业提供支持,并有效识别铺管过程的潜在风险。采用铺管软件OFFPIPE建立海底管道铺设模型,对陆丰7-2海底管道铺设张力、水深和托管架角度等参数敏感性进行了分析,明确了蓝疆号铺管船的铺管作业参数,为安全可靠地铺设海底管道提供了技术支持。     

水下油气泄漏声学探测实验

如何快速有效探测识别水下油气泄漏是目前亟需解决的技术难题。通过实验选取5种油样和2种沉积物布设不同直径、含油量的探测目标,并通过多波束声呐在水池内开展60组声学探测实验。实验表明,海底含油沉积物与海底沉积物的散射强度差值为10 dB,水柱中的油气与水体背景的散射强度差值为7 dB。声学探测是油气泄漏探测的有效方法。     

连云港徐圩海域海岸性质研究

研究了连云港徐圩海域底质的粒径特征和泥沙水力特性,并与连云港主港区、天津港和黄骅港等港口进行对比,研究了不同海岸类型在底质的粒径特征和泥沙水力特性的差异,指出泥沙颗粒黏性影响泥沙水力特性、泥沙水力特性决定海岸性质,给出了海岸性质分类的改进意见,在此基础上确定了徐圩海域海岸性质.     

Distribution of suspended sediment in the coastal sea off the Ganges–Brahmaputra River mouth: observation from TM data

Remote sensing technique was applied to estimate suspended sediment concentration (SSC) and to understand transportation, distribution and deposition of suspended sediment in the estuary and throughout the coastal sea, off the Ganges–Brahmaputra River mouth. During low river discharge period, zone of turbidity maximum is inferred in the estuary near the shore. SSC map shows that maximum SSC reaches 1050 mg/l in this period. Magnitude of SSC is mainly owing to resuspension of the bottom surface sediments induced by tidal currents flowing over shallow water depths. The influence of depth on resuspension is farther revealed from the distribution and magnitude of SSC along the head of Swatch of No Ground (SNG) submarine canyon. During high river discharge period, huge river outflow pushed the salt wedge and flashes away the suspended sediments in the coastal sea off the river mouth. Zone of turbidity maximum is inferred in the coastal water approximately within 5–10 m depth of water, where the maximum SSC reaches 1700 mg/l. In this period, huge fluvial input of the suspended sediments including the resuspended bottom sediments and the particles remaining in suspension for longer period of time since their initial entry control mainly the magnitude of SSC. In the estuary near the shore, seasonal variation in the magnitude of SSC is not evident. In the coastal sea (>5 m water depth), seasonal influence in the magnitude of SSC could be concluded from the discrepancy between SSC values of two different seasons. Transportation and deposition of suspended sediments also experiences seasonal variations. At present, suspended sediments are being accumulated on the shallow shelf (between 5 and 10 m water depth) in low discharge period and on the mid-shelf (between 10 and 75 m water depth) during high discharge period. An empirical (exponential) relationship was found between gradual settle down of suspended sediments in the coastal sea and its lateral distance from the turbidity maximum.     

水域交通危险度的模糊综合评判法

长期的事故统计数据，是交通环境、水域特征、航道特点、水文气象等各种因素的综合反映，而这些因素正是评判水域交通危险度的主要指标。而且，利用事故统计数据得到的评价结果也包含了操船者在这一水域的行为因素。为此，本文提出基于事故统计数据的水域交通危险度的多层次模糊综合评判法，并给出评判模型及评判实例。     

潜艇大攻角操纵运动预报

舱室破损进水是造成潜艇失事的主要险情之一.文中针对潜艇首部破损进水并采取应急吹除上浮时出现的大攻角运动状态,建立了潜艇大攻角操纵运动数学模型.通过数学模型中有、无考虑大攻角水动力修正的两种形式,对潜艇首部舱室破损进水的挽回操纵进行了仿真预报比较.仿真结果表明,潜艇在大攻角状态下的操纵运动预报,数学模型中考虑了大攻角水动力修正后的预报更加合理.而且,在潜艇舱室破损进水采取应急吹除挽回时,需要重点关注升降舵对纵倾的控制.     

Methane release and coastal environment in the East Siberian Arctic shelf

In this paper we present 2 years of data obtained during the late summer period (September 2003 and September 2004) for the East Siberian Arctic shelf (ESAS). According to our data, the surface layer of shelf water was supersaturated up to 2500% relative to the present average atmospheric methane content of 1.85 ppm, pointing to the rivers as a strong source of dissolved methane which comes from watersheds which are underlain with permafrost. Anomalously high concentrations (up to 154 nM or 4400% supersaturation) of dissolved methane in the bottom layer of shelf water at a few sites suggest that the bottom layer is somehow affected by near-bottom sources. The net flux of methane from this area of the East Siberian Arctic shelf can reach up to 13.7 × 10⁴ g CH₄ km^− 2 from plume areas during the period of ice free water, and thus is in the upper range of the estimated global marine methane release. Ongoing environmental change might affect the methane marine cycle since significant changes in the thermal regime of bottom sediments within a few sites were registered. Correlation between calculated methane storage within the water column and both integrated salinity values (r = 0.61) and integrated values of dissolved inorganic carbon (DIC) (r = 0.62) suggest that higher concentrations of dissolved methane were mostly derived from the marine environment, likely due to in-situ production or release from decaying submarine gas hydrates deposits. The calculated late summer potential methane emissions tend to vary from year to year, reflecting most likely the effect of changing hydrological and meteorological conditions (temperature, wind) on the ESAS rather than riverine export of dissolved methane. We point out additional sources of methane in this region such as submarine taliks, ice complex retreat, submarine permafrost itself and decaying gas hydrates deposits.     

An Alert System for Beach Hazard Management in the Balearic Islands

A real-time beach hazard level associated with nearshore hydrodynamics is presented in this article. The suitability of the discussed alert system is illustrated via its application to fifteen beaches in the Balearic Islands (Western Mediterranean Sea) providing nearshore safety conditions for beach safety manager. The system provides daily forecasts of nearshore wave conditions using the deep water wave forecasts. The shallow water wave data (wave height, period, and direction) together with the morphology of the site (presence of bars, capes, beach type, etc.) are used to define a hazard level (low, medium, and high) associated with local conditions. The resulting hazard level is transmitted via SMS to lifeguards and local authorities for real-time beach management. The low computational cost of this system after the initial implementation and subsequent calibration results in a very suitable approach for beach management in order to mitigate risks related to local hydrodynamics.     

深挖沟铺管技术在渤西南联网供气项目上的应用

海底管道的铺设有很多种挖沟方法,因海水深度,地质条件等情况的不同,采用的方法也不相同。渤西南联网供气项目为避免锚地的各类船只抛描破坏,保证海管的安全,海洋石油工程股份有限公司和天津俊昊海洋工程有限公司在海底管道铺设和后挖沟施工中进行合作,采用接触式潜水射流喷冲气举式挖沟机(此系专利设备),首次成功完成了国内海管埋深达到4米的深挖沟作业。通过这次深挖沟埋管的实施,证明这种新的工艺,可以应用到更多的海底管道深挖沟埋管工程中,也可以应用到海管穿越航道、锚地等类似的既要保护管道又要保证通航安全的管道施工工程中。     

海外工程选址中的地质分析

介绍在伊朗某大型LNG液化厂工程建设场地选址中,应用地质分析结合经济分析对比快速选出最优场址的过程。通过收集拟选定的A、B场址的已有地质资料,结合现场地质调查,得出各拟选场址的地质特点,认为场地中砂、钙质胶结和暗礁等对场地平整、地基处理、桩基及沉桩工艺、航道开挖、主码头建设、电厂和液化厂动力基础等影响重大,是影响工程造价的核心。通过对比,得出B地块是最优的场址的结论。     

一种船用直升机电源负载模拟装置设计

根据船用直升机负载性能特点，分析负载模拟装置的设计要求，从负载容量及分组、散热功能、控制保护功能、结构布置等多个方面对负载模拟装置进行综合设计，并通过工程样机开展试验，验证设计方案的可行性。该装置可为船用直升机电源的性能验证提供精确可靠的试验保障。