Fluid Mud Measurement and Siltation Analysis in A Trial Excavated Channel in the Approach Channel of the Xiangshan Port

In order to clarify the distribution and variation of silt and fluid mud in the Waiganmen shallow section of the 50000-ton intake channel of the Xiangshan Port, and to understand the influence of the channel excavation on the surrounding flow conditions and the strength of the backsilting, especially the impact of typhoon on the sudden silting of the channel, so as to demonstrate the feasibility and stability of the channel excavation. The fluid mud,hydraulic, sediment and topographic measurements were carried out in the study area, and the thickness of the fluid mud layers, tidal current, sediment and topographic data were obtained. Dual-frequency sounder, gamma-ray densitometer and SILAS navigational fluid mud measurement system were used to monitor the fluid mud, and the results were compared and verified. The adaptability and accuracy of the three methods were analyzed. The SILAS navigational continuous density measurement system and gamma-ray fixed-point fluid mud measurement are used to detect the density, thickness and variation of the fluid mud accurately. Based on the hydrological observation data,the process of erosion and deposition in excavation channel and its influence mechanism are analyzed, and the distribution characteristics and evolution law of siltation in engineering area are given in the form of empirical formula. The research shows that the super typhoon can produce large siltation, which results in sudden siltation of the channel. The tidal current is the main dynamic factor of the change of erosion and siltation of the excavation trench. Under the influence of reciprocating tidal current and excavation topography, the trial excavation trench is silted on the whole. There is fluid mud in the monitoring area of the trench, and the distribution of fluid mud is different in space. The thickness of the fluid mud at the bottom of the trench is generally larger than that outside the trench and the slope of the trench, and the siltation of the trench tends to be slow. The research results can provide scientific evaluation for channel excavation and maintenance, and support for the implementation of the project.     

Modelling of wave damping at Guyana mud coast

The Guyana coastal system is characterized by very thick deposits of Amazon mud and high mud concentrations in its coastal waters. The mud deposits can be quite soft and may liquefy under incoming waves. Subsequently, the liquefied mud damps the incoming waves effectively. This paper presents a simple model to predict wave attenuation over soft (fluid) mud beds. This model is based on the two-layer approach by Gade [Gade, H.G., 1958, Effects of a non-rigid, impermeable bottom on plane surface waves in shallow water, Journal of Marine Research, 16 (2) 61–82.] which is implemented in the standard version of the state-of-the-art wave-prediction model SWAN. Input to the mud wave damping module consists of the extension, thickness, density and viscosity of the liquefied (fluid) mud layer.     

Rheological Properties and Incipient Motion of Cohesive Sediment in the Haihe Estuary of China

The Haihe cohesive sediment, which is typical in China, is studied systematically for its basic physical and incipientmotion properties. Following the requirements of dredging works in the Haihe Estuary, cohesive sediment samples weretaken from three locations. Laboratory experiments were conducted to determine the rheological properties of these sam-ples and to examine the incipient motion of the cohesive sediment. It is found that the cohesive sediment has an obviousyield stress τb, which increases with the mud density in a manner of an exponential function, and so does the viscosityparameter η. The cohesive sediment behaves like a Bingham fluid when its density is below 1.38 ～ 1.40 g/cm3, andwhen denser than these values, it may become a power-law fluid. The incipient motion experiment also revealed that theincipient velocity of the cohesive sediment increases with the density in an exponential manner. Therefore, the incipientmotion is primarily related to the density, which is different from the case for non-cohesive sediment in which the incipi-ent motion is correlated with the diameter of sand particles instead. The incipient motion occurs in two different ways de-pending on the concentration of mud in the bottom. For sufficiently fine particles and a concentration lower than1.20 g/cm3, the cohesive sediment appears as fluidized mud, and the incipient motion is in the form of instability of aninternal wave. For a higher concentration, the cohesive sediment appears as general quasi-solid-mud, and the incipientmotion can be described by a series of extended Shields curves each with a different porosity for newly deposited alluvial mud.     

A Bingham-plastic model for fluid mud transport under waves and currents

Simplified equations of fluid mud motion, which is described as Bingham-Plastic model under waves and currents, are presented by order analysis. The simplified equations are non-linear ordinary differential equations which are solved by hybrid numerical-analytical technique. As the computational cost is very low, the effects of wave current parameters and fluid mud properties on the transportation velocity of the fluid mud are studied systematically. It is found that the fluid mud can move toward one direction even if the shear stress acting on the fluid mud bed is much smaller than the fluid mud yield stress under the condition of wave and current coexistence. Experiments of the fluid mud motion under current with fluctuation water surface are carried out. The fluid mud transportation velocity predicted by the presented mathematical model can roughly match that measured in experiments.     

长江口北槽浮泥周期性变化初探

根据2000年长江口北槽浮泥的实测资料,分析浮泥厚度和体积等几何尺度随时间的变化,发现长江口北槽浮泥存在日、半月和年际三种周期变化;日周期的变化受潮流动力周期的控制,这是由潮流冲刷浮泥形成的悬沙并再絮凝沉积造成的;半月周期的变化受潮流半月周期变化引起的泥沙供给量的变化控制;年周期的变化主要是由影响细颗粒泥沙絮凝沉积的长江口水温的年度变化所控制,泥沙供给和动力的年周期变化也有一定的影响.     

九龙江口海沧港区17～-18^#码头基槽浮泥成因分析

九龙江口海沧港区因建设17—18^#泊位而开挖的基槽处发育厚层浮泥．通过对该处浮泥及其周边的水体悬浮颗粒、海底表层和沉积物柱状样的激光粒度分析,发现浮泥的颗粒物主要由峰值粒径在7～10μm的粘土粉砂质细颗粒组分构成,但在浮泥层的下部还含有小部分峰值粒径为200—500μm的砂质粗颗粒组分．浮泥中细颗粒组分的粒度特征和水体中的悬浮颗粒、底质沉积物中的细颗粒组分一致,而浮泥中粗颗粒组分的粒度特征,和九龙江口洪水事件成因的中粗砂的粒度特征一致．结合现场调访和水文观测,得出17—18^#泊位基槽处浮泥的成因主要受海沧港区建设过程中产生的大量再悬浮泥沙以及受水下地形的影响,水动力条件适宜悬浮泥沙在17—18^#泊位基槽处聚淤．此外,台风引发的洪水也是增加悬浮泥沙含量的辅助因素．随着海沧港区的建成,水动力条件的改变,17～18^#泊位港池及调头区浮泥的厚度将小于基槽区浮泥厚度．     

Fluid mud dynamics in the Weser estuary turbidity zone tracked by high-resolution side-scan sonar and parametric sub-bottom profiler

Fluid mud in estuarine turbidity maximum zones (TMZ) can pose considerable navigation risks due to potentially substantial reductions in nautical depth, coupled with an inherent difficulty of detection by conventional echo-sounders. Despite intensive research efforts, however, our knowledge about the spatial and temporal dynamics of fluid mud is still not sufficient. In this study, the combined use of a side-scan sonar (Sportscan®, Imagenex) and a parametric sub-bottom profiler (SES-2000®, Innomar Technology GmbH) has proved successful for high-resolution fluid mud detection and volumetric quantification in an estuarine environment. In 2004 and 2005, repeated surveys were conducted in the navigation channel of the upper meso- to lower macrotidal Weser estuary TMZ (German North Sea coast) at different tidal stages and river discharges. Current velocity data were simultaneously collected by 1,200-kHz broadband ADCP (RDInstruments) measurements. Ground-truthing was carried out by means of grab sampling and gravity coring, adapted to fluid mud conditions. It was found that fluid mud occurrence in the Weser estuary is highly variable on time scales of a few hours and spatial scales of several metres. The riverbed is characterised by sand and mud deposits, and a complex morphology including subaqueous dunes and smooth bed deposits intermittently overlain by fluid mud. Thus, a continuous, coherent fluid mud body covering the entire TMZ riverbed was not observed. Rather, spatial distribution was patchy and highly dependent on suspended particulate matter (SPM) concentrations in the water column, as a result of which local fluid mud deposits varied in thickness from centimetres to metres. The formation of fluid mud was largely restricted to slack water, although slack-water conditions were not necessarily associated with large-scale fluid mud appearance. Advective SPM transport of resuspended fluid mud seems to be the most plausible explanation for the high spatial variability observed, even between two successive tides. The amount of fluid mud deposited and resuspended in the course of a tidal cycle can reach several 10s of tons even in small riverbed depressions.     

Changes in seabed morphology, mud temperature and free gas venting at the Håkon Mosby mud volcano, offshore northern Norway, over the time period 2003–2006

The Håkon Mosby mud volcano is a 1.5-km-diameter geological structure located on the Southwest Barents Sea slope at a water depth of 1,270 m. High-definition seabed mapping of the mud volcano has been carried out in 2003 and 2006. A comparative analysis of the bathymetry and backscatter maps produced from the two surveys shows subtle morphological changes over the entire crater of the mud volcano, interpreted to be the consequence of mud eruption events. Mud temperature measurements point to a persistently warm mud at shallow depth in the crater. This is explained by upward fluid advection, rather than conductive cooling of mud flows. The small-scale spatial variability in the temperature distribution may be related to mud outflows or changes in the fluid flow regime. Furthermore, the locations of free gas venting observed in 2006 were found to differ from those of 2003. Our observations of overall similar topographic profiles across the mud volcano in 2003 and 2006 suggest that eruption events would have been modest. Nevertheless, the data bring evidence of significant change in activity even over short time intervals of only 3 years. This may be a characteristic shared by other submarine mud volcanoes, notably those considered to be in a quiescent stage.     

A snapshot of suspended sediment and fluid mud occurrence in a mixed-energy embayment, Tijucas Bay, Brazil

Along the southern Brazilian coast, Tijucas Bay is known for its unique muddy tidal flats associated with chenier plains. Previous field observations pointed to very high suspended sediment concentrations (SSCs) in the inner parts of the bay, and in the estuary of the Tijucas River, suggesting the presence of fluid mud. In this study, the occurrences of suspended sediments and fluid mud were examined during a larger-scale, high-resolution 2-day field campaign on 1–2 May 2007, encompassing survey lines spanning nearly 80 km, 75 water sampling stations for near-bottom density estimates, and ten sediment sampling stations. Wave refraction modeling provided qualitative wave energy estimates as a function of different incidence directions. The results show that SSC increases toward the inner bay near the water surface, but seaward near the bottom. This suggests that suspended sediment is supplied by the local rivers, in particular the Tijucas. Near-surface SSCs were of the order of 50 mg l⁻¹ close to the shore, but exceeded 100 mg l⁻¹ near the bottom in the deeper parts of the bay. Fluid mud thickness and location given by densimetry and echo-sounding agreed in some places, although being mostly discordant. The best agreement was observed where wave energy was high during the campaign. The discrepancy between the two methods may be an indication for the existence of fluid mud, which is recorded by one method but not the other. Agreement is considered to be an indication of fluidization, whereas disagreement indicates more consolidation. Wave modeling suggests that waves from the ENE and SE are the most effective in supplying energy to the inner bay, which may induce the liquefaction of mud deposits to form fluid mud. Nearshore mud resuspension and weak horizontal currents result in sediment-laden offshore flow, which explains the higher SSCs measured in the deeper parts of the bay, besides providing a mechanism for fine-sediment export to the inner shelf.     

高平4水平井组双保钻井液技术

高平4井组水平井主要用于开发安塞长10组油藏。针对该井组上部直罗组和富县组易坍塌、下部地层钻速相对较慢、地层易造浆的特点,研究应用了环保型聚硅酸盐-黄胞胶钻井液体系。该体系具有抑制性强、润滑和剪切稀释性好的特点,有利于安全快速钻井,对环境污染极小。通过小型配浆实验确定钻井液施工方案,中测后稀释钻井液,降低钻井液滤失量和密度,加强固相控制,使用保护油层的酸溶性暂堵剂和降滤失剂,可最大限度地保护油层。     

3-D fluid-mud dynamics in the Jiaojiang Estuary, China

A 3-D model has been developed for the muddy Jiaojiang Estuary and adjoining coastal waters, and verified against field observations. To simulate fluid-mud formation, the model uses a fine resolution grid near the bottom and involves coupling processes between hydrodynamics and fluid mud such as the sediment-induced buoyancy, increasing turbulent kinetic energy sink and kinematic viscosity, mixing by internal waves riding on the lutocline, and non-Newtonian properties of fluid mud. The effective hydrodynamic drag was reduced in the presence of fluid mud. It is shown that the estuary is infilled by tidal pumping and that longitudinal and transversal gradients of suspended sediment concentration, salinity, and currents control the formation of mud banks. Thus a 3-D model is necessary to estimate the fate of mud, although the model results are very sensitive to details of the parameterization of the hydrodynamics-mud feedback processes.     

不同高度潜堤减淤效果水槽实验研究

潜堤高程是淤泥质海岸潜堤设计的关键要素之一。为了确定潜堤高程,首先根据已建潜堤工程的经验分析得出潜堤减淤的主要机理,即主要是阻挡了浮泥或底部高含沙水体直接进入航道和缩短了含沙水体进入航道的时间,进而在长水槽中开展了一系列比对实验,主要研究不同堤顶高程时的水流紊动、堤前浮泥起动、浮泥层厚度变化、堤后航道泥沙落淤情况等,并以此作为比选堤顶高度的基本依据。实验结果表明当相对高度即潜堤高度与堤前水深之比为0.2～0.5时,便有较好的减淤效果。     

Video and field observations of wave attenuation in a muddy surf zone

Besides the different scales within which coastal processes manifest their energy, the majority of the world's coastal regions exhibit forms of sediment heterogeneity that are physically significant. One example of a heterogeneous environment is Cassino beach, located at the southernmost part of Brazil, a fine-grain-sized sandy beach where fluid mud sporadically is transported to the nearshore and eventually onto the beach. At this site in 2005, as part of a field experiment, a video system was installed. Three years after the installation, a large mud transgression event took place in February 2008 and had 5 km of extension. In this context, the goal of the present work is to characterize the mud deposition pattern across the surf zone, describing the consequences of mud on nearshore dynamics using remote sensing techniques, beach profiles and suspended matter concentration. The surveyed beach profiles registered the deposition of fluid mud at the inner surf zone with concentrations up to 12 mg/l. The material was deposited close to the shoreline and had a cross-shore width of 100 m during the first deposition day occupying the entire water column. From surf zone time series of pixel intensity, it was possible to detect the attenuation of the surface wave spectra due to the presence of fluid mud. The combination of video techniques and field data allowed one to follow the formation of a double-layer system, where fluid mud overlays the sandy bottom. The video-based system at Cassino demonstrated that remote detection of fluid mud and quantification of its effect on the nearshore dynamics is feasible. The combination of beach profiles, measurements of suspended matter concentration and intensity timestacks allowed the analysis of the short-term evolution of the mud depositional processes.     

长江河口浮泥形成机理及变化过程

1976年以来，在长江河口盐水楔和最大浑浊带活动的河道进行了20余次现场观测，本文在现场观测资料基础上，确认长江河口浮泥由细颗粒泥沙组成，中值粒径在8－11.5um,小于2um的粘土占28.18%-36.39%,长江河口浮泥是悬沙在盐水混合环境中絮凝沉降于近义廾风暴潮再悬浮泥沙形成的高浓度浑水层，在成因类型上分为憩流浮泥，盐水楔浮泥和风暴潮浮泥，第1种在涨或落潮转流期低流时形成，规模大，厚度薄，第2种在盐水楔发育时形成，规模较小，厚度较大，第3种在大风后形成，规模大，厚度薄，第2种在盐水楔发育时形成，规模较小，厚度较大，第3种在大风后形成，规模大，范围广，若三者相遇，则浮泥厚度和范围最大，浮泥具有枯季，大小潮秽暴周期变化规律，长江河口河道多的浮泥层，浮泥层的变化与河口拦门沙的冲淤有良好的正相关。     

Three generations of mud volcanoes on the Louisiana continental slope

Three mud volcanoes were identified in a small area of the upper continental slope of the Gulf of Mexico. One is actively accreting by small, intermittent eruptions of gas and fluid mud. Eruptions occur from a pool of gas- and oil-saturated muds that upwell and spill over the central crater edge and down the flanks of the coneshaped buildup. A second structure, a possible sand volcano, is in the last stages of activity, with only slight evidence of gas-saturated sediments. The third structure is a dormant mud volcano with furrowed sides and scattered authigenic carbonate plates and rubble but no venting of gas or fluids.     

深水井控中地层呼吸效应的识别与处理探讨

在海洋深水海域,由于其沉积环境的特殊性而使得地层比较脆弱,表现为地层孔隙压力和破裂压力之间的窗口比较窄,在实施钻探作业过程中当循环当量钻井液密度接近于地层破裂压力而超过井周地层的闭合钻井液密度当量,就会形成地层呼吸效应,即正常钻进保持循环时部分钻井液进入井眼附近地层,在接立柱停止循环时这部分钻井液回吐而观察到溢流,从表象上难以判断是地层回吐还是真正发生了溢流,需要频繁使用司钻法循环出溢流来确认,这给井控作业增加额外时间和风险.此文分析了深水地层呼吸效应的形成机理,阐述在深水钻井中如何识别与判断地层呼吸,提出相应的技术措施,为深水钻井作业提供参考.     

Evidence of episodic long-lived eruptions in the Yuma,Ginsburg, Jesús Baraza and Tasyo mud volcanoes,Gulf of Cádiz

High-resolution single channel and multichannel seismic reflection profiles and multibeam bathymetric and backscatter data collected during several cruises over the period 1999 to 2007 have enabled characterising not only the seabed morphology but also the subsurface structural elements of the Yuma, Ginsburg, Jesús Baraza and Tasyo mud volcanoes (MVs) in the Gulf of Cádiz at 1,050–1,250 m water depth. These MVs vary strongly in morphology and size. The data reveal elongated cone-shaped edifices, rimmed depressions, and scarps interpreted as flank failures developed by collapse, faulting, compaction and gravitational processes. MV architecture is characterised by both extrusive and intrusive complexes, comprising stacked edifices (including seabed cones and up to four buried bicones) underlain by chaotic vertical zones and downward-tapering cones suggesting feeder systems. These intrusive structures represent the upper layer of the feeder system linking the fluid mud sources with the constructional edifices. The overall architecture is interpreted to be the result of successive events of mud extrusion and outbuilding alternating with periods of dormancy. Each mud extrusion phase is connected with the development of an edifice, represented by a seabed cone or a buried bicone. In all four MVs, the stacked edifices and the intrusive complexes penetrate Late Miocene–Quaternary units and are rooted in the Gulf of Cádiz wedge emplaced during the late Tortonian. Major phases of mud extrusion and outbuilding took place since the Late Pliocene, even though in the Yuma and Jesús Baraza MVs mud volcanism started in the Late Miocene shortly after the emplacement of the Gulf of Cádiz wedge. This study shows that fluid venting in the eastern sector of the Gulf of Cádiz promoted the outbuilding of large long-lived mud volcanoes active since the Late Miocene, and which have been reactivated repeatedly until recent times.     

Classification of highly turbid Jiaojiang Estuary

ThisstudywassupportedbytheNationalNaturalScienceFoundationofChinaundercontractNo.49276274,theZhejiangProvinceNaturalScienceFoundationundercontractNo.490013,theChina-Australiabilateralscienceandtechnologyprogram,theAustralianInstituteofMarineScience,theModellingLaboratoryoftheMarineScienceintheSecondInstituteofOceanographyoftheStateOceanicAdministration.INTRODUCTIONTheJiaojiangEstuaryis1ocatedintheeasterncoastofChina,2OokmfromthesouthoftheChangjiangRiver(YangtzeRiver),linkedin…     

波浪作用下浮泥悬扬浓度特性研究

为研究不同波浪环境下,水底浮泥层产生泥沙悬扬后其浓度的分布特性,使用浊度计测定浊度的方法确定水体中泥沙的浓度,并在水槽实验中改变水深、浮泥厚度及造波机的频率和振幅,观察水槽中悬浮泥沙浓度的变化情况,获得水深、波浪频率、波幅以及浮泥厚度对底床泥沙悬扬的影响,分析泥沙浓度的垂向分布特征等。实验结果显示,水深对底床泥沙悬扬的影响最为显著,其他实验参数的影响均不十分显著。同时,通过垂向输沙平衡的分析,得到一个可描述泥沙垂向浓度分布的理论公式,并利用水槽实验结果进行验证。对比结果显示,理论公式所得曲线与实验结果曲线变化趋势一致,部分工况下,理论值稍稍偏大。     

Cyclic activity of mud volcanoes: Evidences from Trinidad (SE Caribbean)

Fluid and solid transfer in mud volcanoes show different cyclic phases of activity, including catastrophic events and periods of relative quiescence characterized by moderate activity. This is notably well-shown by the compilation of historical data onshore Trinidad. It appears that each eruptive mud volcano has its own period of catastrophic activity, and this period is variable from one volcano to another. The frequency of the eruptions seems essentially controlled by local pressure regime within the sedimentary pile. The dynamics of expulsion of the mud volcanoes during the quiescent phases has been studied with the help of temperature measurements within the mud conduits. The mud temperature in these conduits is notably concurrently controlled by the gas flux (endothermic gas depressurizing induces a cooling effect), and by the mud flux (mud is a vector for convective heat transfer). Complex temperature distribution was observed in large conduits and pools. Especially in the bigger pools, the temperature distribution characterizes convective cells with an upward displacement of mud above the deep outlet, and ring-shaped rolls associated with the burial of the mud on the flanks of the pools. In tube-like shaped narrow conduits, the temperature is more regular, but we observed different types of profiles, with either downward increasing or decreasing temperatures. Near constant to even negative gradients compared to the general temperature gradient are typical for very dynamic fluid systems. The temperature profiles varied from one place to another, as well as over time. The temperatures measured within the conduits and their base show that the fluid flow is not constant but highly variable through short time-periods. We observed locally a significant daily change of the temperature of the expelled mud which shows also that the mud flux is changing very rapidly due to the migration dynamics of the mud in fracture systems. We also observed very short time-period cyclic variations with a frequency of several minutes. These high frequencies temperature changes could be related to the dynamics of two-phase flows (gas and mud) through the mud volcano conduits.