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11.
An assessment model for the fate and environmental effects of offshore drilling mud discharges 总被引：1，自引：0，他引：1
Charles G. Hannah Adam Drozdowski John Loder Kee Muschenheim Tim Milligan 《Estuarine, Coastal and Shelf Science》2006,70(4):577
The benthic boundary layer transport (bblt) model was developed to assess potential impact zones from drilling mud discharges from offshore oil and gas drilling. The model focuses on the drift, dispersion and concentration levels of the suspended fraction of the drilling mud fines in the benthic boundary layer with the assumption of a spatially homogeneous environment. The current version of the model includes a wave boundary layer, a breakup module for drilling mud flocs, a dose–response module for scallops, and a graphical user interface (GUI). The GUI was written in Java which makes the code largely platform independent. Simulations of suspended barite concentration near Sable Island on the Scotian Shelf during drilling in the fall of 1999 reproduce the very low concentrations (generally less than 1 μg L−1) observed during the Environmental Effects Monitoring program. However, the simulations also exhibited concentrations in excess of the no-effects concentration for scallops (100 μg L−1) prior to the sampling program. The model estimates that the potential impact on scallops in the vicinity of the drilling is a few days of lost growth over scales of a few kilometers. 相似文献
12.
The present paper is Part I of a series of three papers prepared by the authors on the methods useful for ultimate limit state assessment of marine structures, that have been developed in the literature during the last few decades. It is considered that such methods are now mature enough to enter day-by-day design and strength assessment practice. The aims of the three papers are to conduct some benchmark studies of such methods on ultimate limit state assessment of (unstiffened) plates, stiffened panels, and hull girders of ships and ship-shaped offshore structures, using some candidate methods such as ANSYS nonlinear finite element analysis (FEA), DNV PULS, ALPS/ULSAP, ALPS/HULL, and IACS common structural rules (CSR) methods. As an illustrative example, an AFRAMAX-class hypothetical double hull oil tanker structure designed by CSR method is studied. In the present paper (Part I), the ultimate limit state assessment of unstiffened plates under combined biaxial compression and lateral pressure loads is emphasized using ANSYS, DNV PULS, and ALPS/ULSAP methods, and their resulting computations are compared. Part II will deal with methods for the ultimate limit state assessment of stiffened panels under combined biaxial compression and lateral pressure using ANSYS, DNV PULS, and ALPS/ULSAP methods, and Part III will treat methods for the progressive collapse analysis of the hull structure using ANSYS, ALPS/HULL, and IACS CSR methods. 相似文献
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The geostatistical approach was applied to integrate MT (Magneto-telluric) resistivity data and borehole information for the spatial RMR (Rock Mass Rating) evaluation. Generally, resistivity of the subsurface is believed to be positively related to the RMR, thus the resistivity and borehole RMR information was combined in a geostatistical approach. To relate the two different sets of data, the MT resistivity data were used as secondary information and the RMR mean values were estimated at unsampled points by identification of the resistivity to the borehole data. Two types of approach are performed for the estimation of RMR mean values. Then the residuals of the RMR values around the borehole sites are geostatistically modeled to infer the spatial structure of difference between real RMR values and estimated mean values. Finally, this geostatistical estimation is added to the previous means. The result applied to a real situation shows prominent improvements to reflect the subsurface structure and spatial resolution of RMR information. 相似文献
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Environmental justice is the principle that environmental costs and amenities ought to be equitably distributed within society. Due to the ethical, political, and public–health implications, and because many choices confront those researching environmental justice, standardized measures are needed to inform public dialogue and policy. We develop and test seven indices on three Colorado cities to measure the relationship between the distribution of environmental hazards and minority and poverty–stricken populations, and recommend the Comparative Environmental Risk Index as a preliminary, standardized measure for comparing urban areas. This index is particularly relevant to disadvantaged communities, regional planning organizations, environmental–justice networks and scholars, and state and federal agencies. 相似文献
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A disaggregation method used by the UK water industry to disaggregate simulated hourly data to the 5-min time-scale is examined using data from Heathrow (London). This analysis shows the shortcomings of this algorithm, both in reproducing the temporal structure of rainfall depths and generating extreme events. An alternative method is proposed, based upon a random cascade with a log-Poisson generator. This is a parsimonious model requiring only two parameters per season. It is shown to provide a clear improvement upon the existing disaggregator, both in terms of temporal structure and extreme behaviour. It could thus be a powerful tool for urban hydrology which requires data at fine time-scale for design purposes and simulation studies. The utility of such a tool depends upon its potential for operational use, i.e., for implementation without any fine-scale data. The model's performance is found to be maintained when hourly rainfall time series are the only available data. 相似文献
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The present paper is Part III of a series of three papers on the methods useful for ultimate limit state assessment of ships and ship-shaped offshore structures. It is focused on the methods for the progressive collapse analysis of hull girders under bending moments, in contrast to the previous two papers (Parts I and II), respectively, dealing with methods for the ultimate limit state assessment of unstiffened plates and stiffened panels. An AFRAMAX-class hypothetical double hull oil tanker structure designed by IACS common structural rules (CSR) method is studied as an illustrative example. The ultimate vertical bending moment capacity of the hull structure is then analyzed by ANSYS FEA, ALPS/HULL, and IACS CSR methods, and their resulting computations are compared. 相似文献
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Compensation for differential code bias (DCB) is necessary because it is the major source of errors in total electron content (TEC) measurements. The DCB estimation performance is degraded when only the regional GPS network is used. Because DCB estimation is highly correlated with ionospheric modeling, this degradation is particularly evident for measurements concentrated in an area of high TEC concentration. This study proposes a DCB estimation method that uses the long-term stability of the DCB to improve the estimation performance of the regional GPS network. We estimate satellite DCBs by assuming their constancy over seven months. This extended period increases the number of measurements used in DCB estimation and changes the local time distribution of collected measurements. As a result, the unbalanced distribution of specific ionospheric conditions disappears. Tests are performed using both global and regional networks, and the estimation performance is evaluated based on the position error and pseudorange residuals. First, the difference between the global and regional networks when using the conventional method is analyzed. Second, proposed methods are applied to regional networks. The proposed method can improve the DCB estimation performance, and the results are similar to those obtained using one-day global network data. 相似文献
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The seakeeping characteristics of various boom geometries in irregular waves and currents are investigated. The response of a floating boom section on the open sea is a function of a number of parameters, such as boom geometry, distribution of mass, buoyancy/weight ratio, and wave and current characteristics. To understand the relationship between these design parameters more clearly, a series of regular and irregular wave tests were conducted with six different 1:4 scale models for three current velocities and six different wave conditions. To simplify the problem, only rigid boom sections consisting of a buoyancy cylinder and vertical skirt were used. In parallel with this experimental program, a numerical model for the responses of two-dimensional floating boom sections in small-amplitude waves is also developed. The numerical results are compared with our large-scale experimental results. The boom effectiveness on the open sea is evaluated based on the concept of “effective draft” and “effective freeboard” assuming that drainage and oversplashing failures are the prime mechanisms of containment failure. Using the present results, a guideline for the optimum design/selection of future booms is developed. 相似文献
20.
A practical estimation of Clark IUH parameters using root selection and linear programming 总被引：1，自引：0，他引：1
The values of the parameters of the Clark instantaneous unit hydrograph (IUH) are often relying on the subjective decision of the researcher, which leads to large variations of their values. Therefore, an objective method minimizing the subjective judgement in the IUH modelling procedure while providing a reduced range of acceptable values is proposed. The proposed method uses a basin average IUH to mitigate the robustness problem of the Clark IUH parameters. Using linear system theory, the z‐transform is applied to the average IUH and then the IUH polynomial is factored into the recession and time‐area curve (TAC) components based on a convolution relation between the Clark IUH parameters. During this calculation, the root selection method was adopted to verify the storage coefficient R from the recession component and a linear programming technique was applied for determining the TAC for the basin of interest. The Wi River basin was used to test the applicability of the proposed method. The results showed that the components of a single reservoir and the TAC for Clark IUH were separated effectively, and acceptable values for the parameters were obtained. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献