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61.
根据中、日合作黑潮调查研究期间(1987-1993年)在九州西侧海域获得的水文资料,计算了129°E断面的地转流速和流量。着重提出129°E断面北侧存在一支较稳定的西向流;分析这支西向流的去向,指出它是向对马暖流输送黑潮水的重要途径;给出了这支西向流及黑潮通过该断面的流速、流轴、流幅及流量的变化特征。 相似文献
62.
根据浅水波浪的底摩擦效应,对鲁南灵山湾和臼-岚山镇近岸区进行了波浪的海底摩擦力计算。波浪的海底摩擦力等值图与已知滨海锆石砂矿资料对比表明,底摩擦力大于0.18N/m^2的动力分选区有利于重矿物砂富集。据此,进一步预测了鲁南近岸带的砂矿富集区。 相似文献
63.
64.
Estimation of Land Subsidence Based on Groundwater Flow Model 总被引:8,自引:0,他引:8
This article presents an approach for estimating land subsidence due to withdrawal of groundwater. The proposed method calculates the groundwater seepage in 3-D-condition and calculates the land subsidence one-dimensionally. The governing equation on groundwater seepage is based on the three-dimensional mass conservation law and the principle of effective stress. The land subsidence calculation method is derived based on the following assumptions: (1) displacements occur only in the vertical direction, and (2) in vertical direction the total stresses do not change. The governing equation is solved by numerical method, i.e., finite element method (FEM) in spatial discretization and finite difference method (FDM) in time series discretization. In FEM Galerkin method is adopted and in FDM, lumped matrix method is employed. The proposed method is calibrated via analyzing 1-D consolidation problem and the results are compared with those from Terzaghi's one-dimensional consolidation theory and oedometer test. The proposed method is employed to analyze the consolidation of a soft layer due to withdrawal of groundwater from an aquifer under it. Moreover, this method is also applied to a field case of land subsidence due to groundwater pumping in a gas production field in Japan. The analytical results are compared with the field observed data. The results show that this approach simulates the field case well. 相似文献
65.
66.
Sediment movement under unidirectional flows: an assessment of empirical threshold curves 总被引:1,自引:0,他引:1
D. Paphitis 《Coastal Engineering》2001,43(3-4)
A selection of threshold data sets from previous investigations is used to re-examine, selectively, some of the empirical curves that are most commonly used for the prediction of sediment threshold. Simple analytical formulae are derived describing single line curves for mean threshold values and envelopes for the initial movement of discrete particles and the commencement of mass sediment transport phases of the critical condition.The complexity of factors governing the prevailing conditions at threshold, together with the randomness of events, limits deterministic solutions; however, the curves provide an approach that can be used readily in practical applications. In contrast, the envelope presentation is more of a stochastic approach to the definition of threshold. It recognises that there is no definitive threshold condition under which a particular particle size can be displaced, but rather that a range of threshold values exist.The empirical threshold relationships were derived on the basis of a relatively large amount of data. However, the sources utilised have interpreted the ‘critical condition’ in various ways, implying that the formulae must be treated with caution in applications. 相似文献
67.
K. K. Balachandran 《Estuarine, Coastal and Shelf Science》2004,59(4):589-598
Coastal waters off the southwest coast of India draw special attention because of the occurrence of mud banks at certain locations during southwest monsoon period. The present study puts forward a hypothesis of a subterranean flow, which could be a plausible mechanism to initiate the mud banks. The subterranean flow is believed to be coupled with activated trending faults and originate from the adjacent watershed (Vembanad Lake) separated from the sea by a narrow strip of land where submerged porous lime shell beds are present. When the lake water injection occurs through the fault, the mud/clay gets excited by its thixotrophic properties (as the overlying water looses its electrolyte) and transforms into a flowing fluid. The lowering of salinity due to the introduction of fresh water keeps the mud suspension in the water column for longer duration, leading to the formation of mud banks. The idea of subterranean flow through lime shell beds initiating formation of mud banks may apply globally to any coastal regions hugged by wetlands and of similar geological conditions. 相似文献
68.
LIANGDong-fang CHENGLiang KervinYEOW 《中国海洋工程》2005,19(2):269-286
A numerical model for the self-burial of a pipeline trench is developed. Morphological evolutions of a pipeline trench under steady-current or oscillatory-flow conditions are simulated with/without a pipeline inside the trench. The oscillatory flow in this study represents the action of waves. The two-dimensional Reynolds-averaged continuity and Navier-Stokes equations with the standard k-e turbulence closure, as well as the sediment transport equations, are solved with the finite difference method in a eurvilirrear coordinate system. Both bed and suspended loads of sediment transport are included in the morphological model. Because of the lack of experimental data on the backfilling of pipeline trenches, the numericalmodel is firstly verified against three closely-relevant experiments available in literature. A detailed measurement of the channel migration phenomenon under steady currents is employed for the assessment of the integral performance of themodel. The two experimental results from U-tube tests are used to validate the model‘s ability in predicting oscillatory flows. Different time-marching schemes are employed for the morphological computation under unidirectional and oscillatory conditions. It is found that vortex motions within the trench play an important role in the trench development. 相似文献
69.
70.
江西省永平铜矿西部排土场极限堆载高度确定 总被引:2,自引:0,他引:2
国内外对排土场极限堆载高度的理论计算缺乏研究,目前尚无成熟的统一理论计算方法。文章结合永平铜矿西部排土场的工程实例,在进行边坡工程地质条件勘察与排土场岩土物理力学性质试验研究的基础上,采用数值计算方法对排土场进行了分层堆载数值模拟计算。通过对计算结果的分析,得到位移、塑性区与安全系数随堆载高度的变化规律,并确定了该排土场的极限堆载高度。 相似文献