Recent advances in offshore geotechnics for deep water oil and gas developments   总被引：3，自引：0，他引：3  

Mark F. Randolph  Christophe Gaudin  Susan M. Gourvenec  David J. White  Noel Boylan  Mark J. Cassidy 《Ocean Engineering》2011,38(7):818-834

The paper presents an overview of recent developments in geotechnical analysis and design associated with oil and gas developments in deep water. Typically the seabed in deep water comprises soft, lightly overconsolidated, fine grained sediments, which must support a variety of infrastructure placed on the seabed or anchored to it. A particular challenge is often the mobility of the infrastructure either during installation or during operation, and the consequent disturbance and healing of the seabed soil, leading to changes in seabed topography and strength. Novel aspects of geotechnical engineering for offshore facilities in these conditions are reviewed, including: new equipment and techniques to characterise the seabed; yield function approaches to evaluate the capacity of shallow skirted foundations; novel anchoring systems for moored floating facilities; pipeline and steel catenary riser interaction with the seabed; and submarine slides and their impact on infrastructure. Example results from sophisticated physical and numerical modelling are presented.  相似文献   

Modeling the onset of photosynthesis after the Chicxulub asteroid impact     

Noel Perez  Rolando Cardenas  Osmel Martin  Reinaldo Rojas 《Astrophysics and Space Science》2013,343(1):7-10

We do a preliminary modelling of the photosynthetic rates of phytoplankton at the very beginning of the Paleogene, just after the impact of the Chicxulub asteroid, which decisively contributed to the last known mass extinction of the Phanerozoic eon. We assume the worst possible scenario from the photobiological point of view: an already clear atmosphere with no ozone, as the timescale for soot and dust settling (years) is smaller than that of the full ozone regeneration (decades). Even in these conditions we show that most phytoplankton species would have had reasonable potential for photosynthesis in all the three main optical ocean water types. This modelling could help explain why the recovery of phytoplankton was relatively rapid after the huge environmental stress of that asteroid impact. In a more general scope, it also reminds us of the great resilience of the unicellular biosphere against huge environmental perturbations.  相似文献   

Marine cements in mid-Tertiary cool-water shelf limestones of New Zealand and southern Australia   总被引：1，自引：0，他引：1  

Campbell S. Nelson  & Noel P. James 《Sedimentology》2000,47(3):609-629

Large areas of southern Australia and New Zealand are covered by mid‐Tertiary limestones formed in cool‐water, shelf environments. The generally destructive character of sea‐floor diagenesis in such settings precludes ubiquitous inorganic precipitation of carbonates, yet these limestones include occasional units with marine cements: (1) within rare in situ biomounds; (2) within some stacked, cross‐bedded sand bodies; (3) at the top of metre‐scale, subtidal, carbonate cycles; and (4) most commonly, associated with certain unconformities. The marine cements are dominated by isopachous rinds of fibrous to bladed spar, interstitial homogeneous micrite and interstitial micropeloidal micrite, often precipitated sequentially in that order. Internal sedimentation of microbioclastic micrite may occur at any stage. The paradox of marine‐cemented limestone units in an overall destructive cool‐water diagenetic regime may be explained by the precipitation of cement as intermediate Mg‐calcite from marine waters undersaturated with respect to aragonite. In some of the marine‐cemented limestones, aragonite biomoulds may include marine cement/sediment internally, suggesting that dissolution of aragonite can at times be wholly marine and not always involve meteoric influences. We suggest that marine cementation occurred preferentially, but not exclusively, during periods of relatively lowered sea level, probably glacio‐eustatically driven in the mid‐Tertiary. At times of reduced sea level, there was a relative increase in both the temperature and the carbonate saturation state of the shelf waters, and the locus of carbonate sedimentation shifted towards formerly deeper shelf sites, which now experienced increased swell wave and/or tidal energy levels, fostering sediment abrasion and reworking, reduced sedimentation rates and freer exchange of sediment pore‐waters. Energy levels were probably also enhanced by increased upwelling of cold, deep waters onto the Southern Ocean margins of the Australasian carbonate platforms, where water‐mass mixing, warming and loss of CO₂ locally maintained critical levels of carbonate saturation for sea‐floor cement precipitation and promoted the phosphate‐glauconite mineralization associated with some of the marine‐cemented limestone units.  相似文献   

Dispersivity Estimates from a Tracer Experiment in a Sandy Aquifer     

Dirk Mallants  Armando Espino  Marijke Van  Hoorick  Jan Feyen  Noel Vandenberghe  Walter Loy 《Ground water》2000,38(2):304-310

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Chlorine-36 in Ground Water Containing Low Chloride Concentrations   总被引：1，自引：0，他引：1  

Stanley N. Davis  June Fabryka-Martin  Laura Wolfsberg  Stephen Moysey  Robert Shaver  E. Calvin Alexander Jr.  Noel Krothe 《Ground water》2000,38(6):912-921

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The palaeomagnetism and magnetic fabric of cave sediments from Grønligrotta and Jordbrugrotta, Norway     

Mark Noel  Shirley St  Pierre 《Geophysical Journal International》1984,78(1):231-239

Summary. Twenty-four oriented specimens of laminated clay were obtained from vertical sections in two caves in northern Norway. Studies of the magnetic remanence and susceptibility anisotropy show that the magnetization is depositional in origin and due to magnetite. The palaeomagnetic record in one section is correlated with results from a Swiss lake sediment core to suggest an age of 9600–6800 yr bp for the cave clay. It is shown that the susceptibility lineation produced on gently sloping surfaces was predominantly controlled by gravity and cannot therefore be used directly to estimate the palaeoflow or palaeofield directions.  相似文献   

    

Douglas M. Hawkins  Noel Cressie 《Mathematical Geology》1984,16(1):3-18

Geological data frequently have a heavy-tailed normal-in-the-middle distribution, which gives rise to grade distributions that appear to be normal except for the occurrence of a few outliers. This same situation also applies to log-transformed data to which lognormal kriging is to be applied. For such data, linear kriging is nonrobust in that (1)kriged estimates tend to infinity as the outliers do, and (2)it is also not minimum mean squared error. The more general nonlinear method of disjunctive kriging is even more nonrobust, computationally more laborious, and in the end need not produce better practical answers. We propose a robust kriging method for such nearly normal data based on linear kriging of an editing of the data. It is little more laborious than conventional linear kriging and, used in conjunction with a robust estimator of the variogram, provides good protection against the effects of data outliers. The method is also applicable to time series analysis.  相似文献   

Culture, nature and landscape in the Australian region     

Noel Castree  Lesley Head   《Geoforum》2008,39(3):1255-1257

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Hot Enough for You? A Spatial Exploratory and Inferential Analysis of North American Climate-Change Projections     

Noel Cressie  Emily L. Kang 《Mathematical Geosciences》2016,48(2):107-121

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Investigation of the atmospheric mechanisms related to the autumn sea ice and winter circulation link in the Northern Hemisphere   总被引：1，自引：0，他引：1  

Martin P. King  Momme Hell  Noel Keenlyside 《Climate Dynamics》2016,46(3-4):1185-1195

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