An investigation into the lateral loading response of shallow bucket foundations for offshore wind turbines through centrifuge modeling in sand

A shallow suction bucket is a new foundation type for offshore wind turbines. Due to its large size and bulky shape, the bucket and the soil within the bucket do not necessarily deform as a whole. Moreover, limited research has been conducted on the hydrodynamic wave influence on the shallow bucket bearing response. These factors pose great challenges to the shallow bucket foundation design. This paper presents a set of centrifuge tests of a shallow bucket model subjected to monotonic and dynamic lateral loads to study the lateral bearing response of shallow bucket foundations in the field under combined loads induced by wind, waves, etc. In addition to the routine measurements (e.g., load-displacement), the soil pressures on the bucket and the distribution and evolution of the excess pore pressures in the surrounding soils are also obtained. The deformation pattern of the bucket (e.g., rotation center) is revealed through displacement measurements. Finally, the proposed easy-to-use analytical equations using the limit equilibrium to assess the bearing capacity of bucket foundations, taking into account the influence of the soil strength degradation caused by hydrodynamic wave loadings, are found to yield good results upon comparison with the centrifuge data, providing useful guidelines for the design of shallow bucket foundations.     

Modeling of vertical heat and moisture transfer and carbon exchange in the soil-vegetation-atmosphere system

A physical and mathematical model of the vertical heat and moisture transfer and the carbon exchange in the soil-vegetation-atmosphere system is proposed that includes the interaction between these processes. The model describes the interception of precipitation by plants and its further evaporation, transpiration, evaporation from a soil surface as well as vertical moisture transfer, photosynthesis, and plant and soil respiration. The model has been verified against data from observations of heat, moisture, and carbon dioxide fluxes at a grassland site (international FIFE experiment, Kansas, United States), in a pine forest (BOREAS, Saskatoon, Canada), and in a broad-leaved mixed forest (FLUXNET measurements in the southeastern United States). Numerical experiments with the models have been conducted to estimate the influence of soil moisture and atmospheric CO₂ concentration on transpiration and carbon exchange of the vegetation cover.     

Local and regional species diversity of benthic Isopoda (Crustacea) in the deep Gulf of Mexico

Recent studies of deep-sea faunas considered the influence of mid-domain models in the distribution of species diversity and richness with depth. In this paper, I show that separating local diversity from regional species richness in benthic isopods clarifies mid-domain effects in the distribution of isopods in the Gulf of Mexico. Deviations from the randomised implied species ranges can be informative to understanding general patterns within the Gulf of Mexico. The isopods from the GoMB study contained 135 species, with a total of 156 species including those from an earlier study. More than 60 species may be new to science. Most families of deep-sea isopods (suborder Asellota) were present, although some were extremely rare. The isopod family Desmosomatidae dominated the samples, and one species of Macrostylis (Macrostylidae) was found in many samples. Species richness for samples pooled within sites ranged from 1 to 52 species. Because species in pooled samples were highly correlated with individuals, species diversity was compared across sites using the expected species estimator (n=15 individuals, ES₁₅). Six depth transects had idiosyncratic patterns of ES₁₅, and transects with the greatest short-range variation in topography, such as basins and canyons, had the greatest short-range disparity. Basins on the deep slope did not have a consistent influence (i.e., relatively higher or lower than surrounding areas) on the comparative species diversity. ES₁₅ of all transects together showed a weak mid-domain effect, peaking around 1200–1500 m, with low values at the shallowest and deepest samples (Sigsbee Abyssal Plain); no longitudinal (east–west) pattern was found. The regional species pool was analyzed by summing the implied ranges of all species. The species ranges in aggregate did not have significant patterns across longitudes, and many species had broad depth ranges, suggesting that the isopod fauna of the Gulf of Mexico is well dispersed. The summed ranges, as expected, had strong mid-domain patterns, contrasting with the local species richness estimates. The longitudinal ranges closely matched a randomized pattern (species ranges placed randomly, 1000 iterations), with significant deviations in the east attributable to lower sampling effort. The depth pattern, however, deviated from the mid-domain model, with a bimodal peak displaced nearly 500 m shallower than the mode of the randomized distribution. The deviations from random expectation were significantly positive above 1600 m and negative below 2000 m, with the result that regional species richness peaked between 800 and 1200 m, and decreased rapidly at deeper depths. The highest species richness intervals corresponded to the number of individuals collected. Residuals from a regression of the deviations on individual numbers, however, still deviated from the randomized pattern. In this declining depth-diversity pattern, the Gulf of Mexico resembles other partially enclosed basins, such as the Norwegian Sea, known to have suffered geologically recent extinction events. This displaced diversity pattern and broad depth ranges implicate ongoing re-colonization of the deeper parts of the Gulf of Mexico. The Sigsbee Abyssal Plain sites could be depauperate for historical reasons (e.g., one or more extinction events) rather than ongoing ecological reasons (e.g., low food supply).     

Interpretation of electric piezocone data of Chennai coast

Geotechnical engineers worldwide practice variety of in-situ techniques to obtain the physical and engineering properties of soil. Electric piezocone, which is an advanced version of cone penetrometer, is capable of measuring cone resistance, sleeve friction and penetration pore pressure. The piezocone test data not only provide valuable information on soil types but are also useful in deriving correlations with the engineering properties of soil for the purpose of analysis and design of foundations. In a view to establish a region-specific correlation between piezocone penetration resistance and soil properties, piezocone tests (CPTu), marine borings, and SPT tests were carried out at seven locations off Chennai, on the east coast of India. CPTu data was used for classifying soil; henceforth expounded that a reasonable classification of soil can be done using cone resistance, sleeve friction, and penetration pore pressure. The available charts to find out the drained shear strength from CPTu data was also verified for the region-specific use. Correlation between cone resistance (q_c), and N-value was established and compared with existing recommendations.     

The use of diagenetic signatures to distinguish marine from continental deposits in Triassic-Jurassic sandstone reservoirs from the UK Central Graben

Poor biostratigraphic control for some Triassic-Jurassic successions in the North Sea Basin and sub-basins necessitates the use of alternative correlation methods. This study examines the use of diagenetic signatures to distinguish continenetal from marine sandstone successions (Triassic-Jurassic) in the UK Central Graben. The key diagenetic alterations encountered in these successions include kaolinitization of the framework grains and the development of sphaerosiderite and pyrite. The δ ¹³C_V-PDB values of siderite (−8.1 to −8.5‰) and of ankerite (−10.8 to −9.2‰), indicate a strong contribution of dissolved carbon from the decay of plant material in soil. However, marine water likely influenced diagenesis during periods of relative sea level rise by providing the dissolved sulfate (SO₄²⁻) required for the precipitation of pyrite. The presence of diagenetic alterations such as kaolinitization of framework grains and cementation by sphaerosiderite could indicate that the sediments were deposited in an overall continental setting. However, the occurrence of pyrite and scattered grains of deep-green colored glauconite suggests occasional marine influence. Such information on the changes of the diagenetic realm provides important clues for establishing a framework for stratigraphic correlations. Caution should be exercised when interpreting petrographic data as subsequent episodes of telodiagenesis can complicate petrographic interpretations.     

Sediment retention at the Changjiang sub-aqueous delta over a 57 year period,in response to catchment changes

The growth of a river delta system is controlled mainly by fluvial sediment discharge and sediment retention in the deltaic areas. In the present study, we attempt to define a sediment retention index, R, and its relation to the deposition rate of the delta. Based upon two assumptions that the amount of the sediment that escapes from the deltaic areas, Q_E, is stationary with minor fluctuations, and that there is a linear relationship between the deposition rate averaged over the sub-aqueous delta (D_av) and the deposition rate at accretion sites within the delta (D_R), the changes in the accretion/erosion patterns of the Changjiang sub-aqueous delta during the period of 1951–2007, in response to river sediment discharge changes, are analyzed. The results show that the sediment retention index can be related to the deposition rate of the sub-aqueous delta; the spatial-temporal distribution pattern of the deposition rate reveals the behaviour of sediment retention of a delta system. For the Changjiang sub-aqueous delta, fluvial sediment discharge data, together with Pb-210 based deposition rates, provide useful information on sediment retention. Changes in the sediment retention index and the accretion/erosion patterns of the sub-aqueous delta have taken place in response to river input changes. In order to improve our understanding of the processes associated with estuarine sediment retention, sediment cores with sufficient spatial coverage may be collected and analyzed to establish accurate Q_E–R and D_av–D_R relationships. In combination with numerical modeling of sediment transport, these relationships form a basis for the analysis of sediment retention mechanisms.     

Seasonal distribution of chlorophyll on mudflats in New South Wales,Australia measured by field spectrometry and PAM fluorometry

Variability of chlorophyll (as an index of micro-algal abundance) between warm and cool seasons at different heights on (distances across) the shore was investigated on intertidal mudflats in warm-temperate Australia. Chlorophyll was measured using ratios of reflectances from field spectrometry and minimal fluorescence (F₀) from PAM fluorometry to compare patterns obtained using these two methods. A single sampling period comprised 2 days of sampling, one for each mudflat, with 2 sampling periods nested within each month, 2 months within each of a cool and warm season in each of 2 years. Large differences in amounts of chlorophyll were found between the two mudflats, although spatial and temporal patterns of variation were generally similar. There were greater amounts of chlorophyll in the cooler months than in the warmer months in each location in each year, which contrasts with many of the patterns reported from elsewhere. There was more chlorophyll on the upper than on the lower shore and the increases from summer to winter were generally greater at the higher levels. Large variation in chlorophyll from week to week within each month demonstrated the need for adequate replication in studies of seasonal patterns of variability. Measurements made by a field spectrometer and a PAM fluorometer were largely consistent, but, at certain times, they showed an opposite pattern. The reasons for these differences were investigated further by looking at differences in other pigments, but the different results from the two methods could not to be explained by changes in composition of the micro-algal assemblage and, as yet, remain unexplained.     

东海盆地丽水凹陷古新统锆石示踪作用分析

锆石具有较强的稳定性，是地质研究中一种强有力的工具。通过对其形态学研究，再结合其地球化学特征，可讨论其母岩的成因；同时，结合颗粒锆石的微区定年，可以讨论重要的地质事件成因和演化，如锆石的成因和微区离子探针技术在研究造山带构造年代学中发挥着重要作用。利用激光探针等离子体质谱(LAM-ICPMS)技术对丽水凹陷古新统沉积岩中锆石进行微区定年和微量元素测定，并对稀土元素配分模式和微量元素特征进行分析，结果表明，对于复杂来源的锆石，利用其地球化学特征进行区分效果不理想，锆石地球化学特征并不是有利的沉积和锆石来源显示。     

Review of nekton patterns and ecological processes in seagrass landscapes

We reviewed seagrass landscape studies on nekton (fish and larger mobile crustaceans) to summarise: (1) patterns of nekton abundance in relation to patch attributes; and (2) models used to explain processes underpinning observed patterns. The response of nekton to landscape attributes is highly variable. Different taxa showed increasing densities with: increasing and decreasing patch size (12 and 11 taxa, respectively), increasing and decreasing proximity within a patch to edge (9, 14), increasing and decreasing distances from nearest seagrass patch (4, 11), and with patches perpendicular and parallel to currents (1, 2). The majority of taxa (213 out of 281, or 82%) showed no relationships. Landscape scale patterns are important for some species but evidence so far does not demonstrate major landscape effects overall. The lack of pattern might reflect the overriding importance of other factors such as within-patch characteristics, water depth or position within an estuary. It might also result from measurements at the wrong scale. The rigour of surveys can be improved by avoiding confounding of patch attributes by other factors, increasing awareness of statistical power, and more considered survey designs for attributes such as edge effects. The predation model is the most frequently invoked and tested model. Other explanatory models are based on disturbance, rates of encounter, food availability, larval supply, migration and reproductive success, but in many cases are not based on observed patterns. The best experimental work has been done on nekton species for which landscape studies have been built on a detailed understanding of the ecology of the species, such as for blue crabs (Callinectes sapidus). As this basic ecological platform is laid for more species, the landscape approach will become increasingly fruitful.     

Estimating horizontal stresses for mudrocks under one-dimensional compression

We examine horizontal stresses in mudrocks for the case of one-dimensional mechanical compression through laboratory measurements of the horizontal to vertical effective stress ratio, i.e. K₀. Previous empirical relationships which predict horizontal stresses as a function of depth or overburden stress are site specific and cannot easily be generalized. The K₀ values of various resedimented mudrocks from a diverse range of geologic origins have been investigated for effective stresses ranging from 0.1 to 100 MPa. The value of K₀ during normal compression (K_0NC) varies systematically as a function of both stress level and mudrock composition. K_0NC generally increases with stress level and values as high as 0.90 have been measured at effective stresses approaching 100 MPa. This finding implies that high horizontal stresses can develop at depth solely due to normal mechanical compression and that tectonic stresses, creep, or geologic unloading are not necessary. Correlations have been developed which allow K_0NC to be estimated from a mudrock's liquid limit, an easily and inexpensively measured property which reflects both the quantity and type of clay minerals present in a mudrock. High liquid limit, smectite-rich mudrocks display a more rapid increase in K_0NC with increasing stress compared to more silty, low liquid limit mudrocks. K₀ measurements made on laboratory resedimented specimens compare well with measurements made on intact core samples as well as in situ tests. Tests carried out to examine K₀ for overconsolidated materials show that K₀ during unloading can be well approximated by a power-law function originally proposed by Schmidt (1966). An original equation is proposed to describe K₀ during reloading. Our experimental results reveal sediment behavior at high stress levels that has not been previously observed and provide useful information on how horizontal stresses evolve within basins.     

杭州湾海底地质灾害初步调查

根据杭州湾近年来工程地质勘察和地球物理探测所获得的资料,将杭州湾常见的地质灾害分为活动性地质灾害和限制性地质灾害.对杭州湾常见的地质灾害因素作了比较深入的分析,特别是潮流冲刷槽、古河道、软土、滑坡、砂土液化、浅层气等与海洋工程密切相关的地质灾害类型及其分布特征、形成机制及危害性等,为本区海洋工程建设和海洋开发提供基础资...     

基于贝叶斯分类器的多普勒天气雷达海浪回波识别和效果检验

为了提升雷达数据质量，减少海浪回波对临近预报和数值天气预报模式的雷达数据同化的不利影响，因此需要对海浪回波进行识别和去除。识别算法主要为统计获得先验概率，分析海浪和降水回波特征分布得到似然函数，再经过贝叶斯分类器来达到识别的目的。在本次算法识别过程中65个样本数据试验的临界成功指数I_CS达到了0.692，结果表明利用贝叶斯分类器对海浪回波的识别，具有较好的识别效果，能一定程度降低海浪回波误判为降水回波的错误，提高雷达数据质量。     

CMIP5模式对青藏高原中东部夏季降水双极型模拟能力的评估

青藏高原中东部夏季降水主要表现为东北和东南反位相变化的双极型特征。采用经验正交函数(empirical orthogonal function,EOF)分解方法,系统性地评估参与第五次耦合模式比较计划 (Coupled Model Intercomparison Project Phase 5,CMIP5)历史模拟试验的 47 个模式对青藏高原中东部夏季降水双极型变化特征的模拟能力。结果表明,大多数模式基本可以反映青藏高原中东部夏季降水东北部和东南部反位相的变化特征。模式间 EOF 分析结果表明在35°N 以南的东西向模拟偏差是 CMIP5 模式模拟降水空间型态的主要偏差,且大多数模式对时间系数的模拟效果差于空间型态。文中定义了一个综合评估指标 Snew 来定量描述模式对空间型态、时间系数以及方差贡献的综合模拟效果。由定量评估结果来看,MIROC-ESM、HadGEM2-CC 和 ACCESS1-0 (FIO-ESM、 HadGEM2-AO 和 MIROC-ESM-CHEM)模式对观测降水的 EOF1(EOF2)模态的综合模拟能力相对较好,而 GISS 系列模式、CESM1-CAM5 和 MPI-ESM-LR (CMCC-CESM、MPI-ESM-MR 和 GFDL- CM3)模式对观测降水的 EOF1(EOF2)模态的综合模拟效果较差。由 EOF1 和 EOF2 的综合评估结果来看,MIROC-ESM-CHEM模式对观测降水的 EOF1 和 EOF2 模态的综合模拟效果最好。     

Observations on some bathypelagic copepods living in British Columbia mainland inlets

Isolated populations of three bathypelagic copepods,Spinocalanus brevicaudatus, Scaphocalanus brevicornis andHeterorhabdus tanneri are shown to exist in the deeper inlets of the British Columbia mainland coast. The three species probably breed throughout the year. The possible significance of some observed migration patterns is discussed. It is shown that useful biological information on bathypelagic organisms can be obtained from relatively accessible and highly productive coastal fjords.     

Nitrous oxide production and denitrification rates in estuarine intertidal saltmarsh and managed realignment zones

Increasing concerns over habitat loss and rising costs of sea defence maintenance due to rising sea levels, has seen increases in the practice of managed realignment and reflooding of former reclaimed areas of intertidal saltmarsh and mudflat around the world. These practices are taking place with little knowledge of their impact on soil biogeochemical processes. Rates of denitrification (using the acetylene inhibition technique) and nitrous oxide (N₂O) production were measured from a long-established saltmarsh (SM) and an adjacent, recently re-flooded managed realignment (MR) site comprising former arable land in the estuary of the River Torridge, Devon, UK. Incubations were carried out in closed chambers in which patterns of tidal flooding were simulated automatically. Measurements were made during periods of flood and non-flood over a total of four tidal inundations with estuarine water. During the latter two flooding episodes floodwater was amended with nitrate (NO₃⁻). Nitrous oxide production in the SM soil generally was lower than in the MR soil, with mean values and standard errors over the whole incubation of 0.27 ± 0.16 mg N₂O-N m⁻² h⁻¹ and 0.65 ± 0.15 mg N₂O-N m⁻² h⁻¹ respectively. Denitrification rates demonstrated a similar trend although generally were an order of magnitude higher than N₂O production, with mean rates and standard errors of 2.88 ± 1.12 mg N₂O-N m⁻² h⁻¹ in the SM soil and 3.39 ± 1.16 mg N₂O-N m⁻² h⁻¹ in the MR soil. The data suggest that both soils are net sinks for NO₃⁻ and net sources for N₂O. Both patterns of tidal inundation and floodwater chemistry affect the process rates in each soil differently. The impact of flooding with NO₃⁻ – amended water was greater on the SM soil than the MR soil, and it is likely that decomposing vegetation buried in the accreting sediments following reflooding at the MR site were supplying a source of N in the soil, and so process rates were less dependent upon external supplies. The act of managed realignment in intertidal zones could therefore result in an increase in mean production of N₂O in intertidal zones, at least in the short term.     

Wind forced circulation and sediment disturbance in a temperate lake

Meteorological forcing on the surface of a lake can generate mixing and transport processes that alter water quality. This study examined how meteorological forcing affected water currents in Lake Rotorua—a large, shallow, temperate, polymictic lake—during a period of sustained vertical mixing and strong winds. Acoustic Doppler current profiler (ADCP) measurements were recorded at two sites and a hydrodynamic model (ELCOM) was used to simulate water movement over the period of ADCP measurements. Model simulations show circulation patterns in Lake Rotorua are strongly influenced by the topography of the lake and, to a lesser extent, the catchment, with little variation in currents with depth during winter mixing. Northeasterly winds produced a clockwise circulation around the mid-lake island with a second anticlockwise gyre between the island and the western shore. This circulation pattern is consistent with topographic gyres found in other large lakes. A shift to a weaker southwesterly wind caused these circulation patterns to reverse direction over a period of c. 6?h, with a weak secondary gyre also occurring within the main anticlockwise circulation. The effect of this circulation pattern on the resuspension of sediment and thus potential in-lake phosphorus control strategies is considered.     

Fractal Characteristics of the Distribution Pattern of Mangrove Bruguiera Gymnorrhiza Populations in Southern China

The distribution patterns of mangrove Bruguiera gvmnorrhiza populations in southern China are analyzed using the box-counting method of fractal theory.The patterns of B.gymnorrhiza populations could be thought of as fractals as they exhibit self-similarity within the range of seale considered.Their fractal dimensions are not integer but fractional.ranging from 1.04 to 1.51.The unoccupied dimensions change from 0.49 to 0.96.The combined conditions of population density.pattern type and aggregation intensity together influence the values of fractal dimensions of patterns.The box counting is a useful and efficient method to investigate the complexity of patterns.Fractal dimension may be a most desirable and appropriate index for quantifying the horizontal spatial microstructure and fractal behaviors of patterns over a certain range of scales.     

New Zealand wave climate from satellite observations

Wave data derived from radar altimeters carried on four satellite missions are combined into a wave climatology for New Zealand waters. These data provide extensive observations of wave conditions around New Zealand, where the paucity of measurements has previously hindered definition of the wave climate. The data span the period 1985 to the present with the exception of a 2‐year gap in 1989–91. The spatial distribution of the long‐term mean of significant wave heights (SWH) indicates a strong latitudinal variation in the south‐west Pacific, with values of over 4 m at latitudes of 50–60°S and under 2.5 m towards the tropics. The shadowing of New Zealand is quite marked; a result of the dominant contribution of south‐westerly wave events. The annual range of the mean SWH also varies over the region; within 0.6 m in the north and 1.3 m in the south. A principal component analysis of the monthly anomalies in mean SWH identifies spatial patterns of variation. Some components vary with the local wind more than others suggesting that some anomalies are associated with wind sea and some with swell. Some patterns also appear to vary with the Southern Oscillation Index and can be related to the wind anomalies associated with El Nino events. Frequency distributions of SWH are also determined, and it is noted that in the north of the region the spatial pattern of the high waves differs considerably from the means.     

Some effects of experimental procedure on settlement of Ostrea Lutaria Hutton

The effect of experimental method on the settlement pattern of Ostrea Iutaria was tested. The intensity of settlement differed with the type of settlement surface and the angle of the surface. The method of arranging the plates, in series or singly, was critical in determining the variation of spatfall with surface angle; the type of plate had no effect on this. Possibly, a factor such as turbulence differences within the plate units affecting free‐swimming larvae about to settle could account for the different settlement patterns but whether these could be caused by a reversal of iesponses or to some passive concentraton mechanism is unknown. Similar variation in experimental techniques probably accounts for most of the conflict in previous reports on the pattern of oyster settlement related to surface angle.     

Numerical simulations of the tidal- and wind-driven circulation in Narragansett Bay

A three-dimensional numerical hydrodynamic model was used to study the tides and certain aspects of the wind-forced flow in Narragansett Bay. The governing equations are solved using the Galerkin-spectral method in the vertical and explicit finite differences in the horizontal and time. A split-mode formulation is used to minimize computational time. Simulations of the M₂ tide gave average errors of less than 2% in amplitude and 2° in phase when compared with observations at 12 tidal-height stations within the Bay. An investigation of the Bay's response to steady, spatially uniform wind forcing indicated that the non-linear interaction between the tidal and wind induced motions strongly affected the predicted steady state current pattern. Calculation of the steady-state wind-induced transports showed that a significant exchange exists between the West Passage, East Passage and Sakonnet River. The dependence of the exchange on the wind magnitude and direction and on the choice of vertical eddy viscosity was investigated. A comparison between modeled results and measurements of current at three locations in the Bay indicated that the model is capable of reproducing some of the features of the wind-induced flow.