南沙群岛永暑礁岩体稳定性评价

永暑礁表层为松散的生物砂砾堆积,表层以下为礁灰岩,夹有2个沉积间断面。礁体呈岩盆结构,从外向内胶结程度依次降低。在综合研究了永暑礁自然环境特征、地层岩性以及岩体结构特征的基础上,认为永暑礁整体稳定性良好,不会发生整体倾覆的现象,浅层土体也不会发生剪切、滑移等工程地质问题。并利用非线性弹性本构模型,对永暑礁礁体地基与边坡在不同应力作用下发生变形与破坏的过程及机理进行了探讨,研究结果认为,在外部应力作用下,珊瑚礁内的应力状态将发生变化,局部出现应力集中,边坡出现拉应力。200kPa的荷载使礁体边坡产生的水平位移小于1cm,岩体边坡仍是稳定的,但最大垂直位移达到1．8cm,有可能出现珊瑚砂的整体剪切破坏。     

塔里木盆地西南缘生物礁特征——以阿尔塔什剖面石炭系和什拉甫组为例

通过野外露头观察与镜下薄片鉴定，综合分析了塔里木盆地西南缘（以下简称塔西南盆地）阿尔塔什剖面石炭系和什拉甫组生物礁沉积特征和成礁模式，认为研究区生物礁为开阔台地内部发育的点礁，分为高凸起型点礁和低凸起型点礁2类；造礁生物为四射珊瑚，附礁生物种类较多，包括腕足类、腹足类、海百合与?类等；生物礁在地貌上呈隆起状，其礁基、礁核、礁盖等亚相清晰。综合研究区生物礁发育特征及古地貌和海平面的演化过程认为：高凸起型点礁是生长在台地内地貌高处的生物礁，随着海平面下降暴露死亡，主要由珊瑚骨架灰岩、含生物碎屑颗粒灰岩组成；低凸起型点礁为在台地内部较为平坦地貌处发育的礁体，因海平面上升被淹死，礁体厚度薄，横向展布广，呈条带状，主要由珊瑚骨架灰岩与生物碎屑泥晶灰岩组成。     

构造运动对生物礁成岩作用的影响——以巴布亚新几内亚合恩晚第四纪珊瑚礁研究为例

对地处新构造运动强烈地区的合恩晚第四纪上升珊瑚阶地三条剖面的样品分析表明:造礁珊瑚和礁灰岩的不稳定矿物成分的转化和成岩强度与构造运动密切相关,而局部气候状况似乎不起主导作用。上升速率较低地区的珊瑚骨骼和礁灰岩的方解石化普遍、彻底,孔隙中方解石胶结物含量大仅存文石胶结物残余;与之相反,构造上升速率高的地区虽有较高的年降雨量,但珊瑚和礁灰岩转化不普遍,方解石胶结物含量低且保存大量文石胶结物。这是因为构造上升决定了阶地的区域地貌特征,影响阶地地形起伏,从而控制了在生物礁成岩变化中起主要作用的水动态条件。     

南沙群岛珊瑚砂工程性质研究

珊瑚砂是发育于热带海洋环境中的一种特殊的岩是质类型,主要由珊瑚碎屑和其他海洋生物碎屑组成,碳酸钙含量高达９６％。特殊的特细胞、结构和发育环境导致珊瑚砂具有独特的工程性质。章综述了珊瑚砂的压缩性、破碎性、剪切特性和强度特笥,指出其显的土力学特点：高孔隙比、高摩擦角和低强度值。颗粒破碎是影响珊瑚太变形和强度特性的主要因素,深入研究珊瑚砂的工程性质对珊瑚岛礁工程设计和施工、加强国防建设、开发热带海洋     

西沙-南沙珊瑚礁礁灰岩抗蚀性特征

台风、风浪、涌浪、风暴潮、天文潮等现象中的气流和水流往往携带大量固体碎屑物,对南海岛礁礁灰岩体产生强烈的侵蚀作用。笔者首先通过珊瑚的磨蚀与压缩实验验证了磨蚀理论的可靠性;其次,由抗压强度和弹性模量定义了具有压强量纲的抗蚀因子,以定量描述岩石抵抗风水侵蚀的能力;最后,对石岛西南端地表风成灰岩进行了初步研究,发现其抗蚀能力较弱。礁灰岩抗蚀性研究将为南海岛礁防护提供一定的科学依据。     

中美洲伯利兹陆架区3个孤立的全新世碳酸盐台地的发育

中美洲伯利兹陆架区３个孤立的全新世碳酸盐台地的发育Ｅ．Ｇｉｓｃｈｌｅｒ,Ｊ．Ｈ．Ｈｕｄｓｏｎ在伯利兹生物礁碳酸盐台地中,通过岩心可以识别出４种全新世岩相：珊瑚粘结灰岩相、颗粒砾状灰岩相、未固结的生物礁砂质和砾质以及泥炭质相。（１）珊瑚粘结灰岩相最为丰...     

南沙群岛珊瑚砂工程性质研究

珊瑚砂是发育于热带海洋环境中的一种特殊的岩土介质类型 ,主要由珊瑚碎屑和其他海洋生物碎屑组成 ,碳酸钙含量高达 96 %。特殊的物质组成、结构和发育环境导致珊瑚砂具有独特的工程性质。文章综述了珊瑚砂的压缩性、破碎性、剪切特性和强度特性 ,指出了其显著的土力学特点 :高孔隙比、高摩擦角和低强度值。颗粒破碎是影响珊瑚砂变形和强度特性的主要因素 ,深入研究珊瑚砂的工程性质对珊瑚岛礁工程设计和施工、加强国防建设、开发热带海洋渔业资源和海底石油资源具有重要的意义。     

南沙群岛珊瑚砂物理力学性质研究

珊瑚砂是发育于热带海洋环境中特殊的岩土介质类型,主要由珊瑚碎屑和其它海洋生物碎屑组成,碳酸钙含量高达96％。特殊的发育环境、物质组成和结构导致了珊瑚砂具有独特的物理力学性质。本文对采白南沙群岛珊瑚岛礁的珊瑚砂样品进行了。系列室内土力学试验,根据试验结果讨论了珊瑚砂的比重、孔隙比、压缩性、破碎性、剪切特性等,指出了珊瑚砂具有不同于石英砂的比重和孔隙比等物理特性,力学性质的特殊性表现在三个方面：内摩擦角大,高压缩性和易破碎。作者认为颗粒破碎是影响珊瑚砂变形和强度特性的主要因素。全面深入地研究珊瑚砂的基本物理力学性质,可为珊瑚岛礁工程建设提供科学合理的设计参数,避免工程事故的发生。     

珊瑚砂动力特性研究进展

综述了颗粒破碎、围压、孔隙水压力、主应力方向等对珊瑚砂动强度、液化特性的影响,总结了珊瑚砂在复杂应力条件和微生物胶结固化后的动力特性研究进展。对珊瑚砂动力特性进一步研究进行了分析,指出应重点研究岛礁珊瑚砂在波浪荷载、爆炸荷载和地震等作用及耦合作用下的动力特性,建立复杂应力条件下考虑珊瑚砂颗粒破碎特性的动本构模型,加强珊瑚砂在地震作用下的液化机理及抗液化工程措施研究,加强岛礁恶劣环境下现场原位试验研究,完善微生物固化珊瑚砂动力特性研究等,不断丰富和完善珊瑚砂动力特性研究成果,为岛礁工程建设服务。     

世界各地的珊瑚礁

在我们生活的地球上,存在着大量的各式各样的珊瑚礁,从而使得水下世界更加绚丽多彩。珊瑚礁蕴藏着丰富的矿产资源。礁灰岩是多孔隙岩类,渗透性好,有机质丰富,是良好的油气生储层;珊瑚灰岩可作为烧制石类、水     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.