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671.
GUAN Yiexiang RONG Fengtao WANG Jingxin YIN Lisheng WANG Hongtu Project Engineer Hydraulic Research Institute Shanxi Province China Vice Chief Engineer Senior Engineer Water Resources 《国际泥沙研究》1991,(1)
In this paper, a numerical model for sedimentation in Fenhe Reservoir and the adjoining reaches has been presented on the basis of the theory of non-equilibrium sediment transport. The model is calibrated by using a part of the sediment data collected for Fenhe Reservoir and checked by simulating the remaining data. Moreover, the method of optimization in nonlinear programming has been applied to determine the basic parameters of the model applying a concept of fuzzy mathematics to formulate the objective functions. The computed amounts of reservoir deposition and channel deformation arc found to be substantially in agreement with the values observed. 相似文献
672.
文章根据对萨拉乌苏河地区第四纪地层中的碎屑矿物分析结果,将重矿物按其抗化学风化的能力不同分为不稳定、较稳定、稳定和极稳定四种类型,不同层位的重矿物类型的百分含量不同,从而可求出重矿物的风化系数HW。不同时期地层的HW不同,而HW的大小变化与化学风化的程度有很大关系,一般来说,化学风化作用强,HW相应变小。而化学风化作用的强弱又主要受气候的影响,从而可推测该时期气候环境的变化。 相似文献
673.
林元武 《地震学报(英文版)》1994,(2)
Fault-weakening effect of reservoir temperature of hot spring and its influence on seismic activities(林元武)Fault-weakeningeffe... 相似文献
674.
675.
T. M. Whitworth 《Environmental Geology》1994,23(1):30-35
Shallow stratigraphic traps exist in certain geologic environments, which might complicate groundwater remediation efforts. Too often, pump-and-treat remediation wells are installed in geometric patterns designed to maximize cleanup operations. If, however, shallow stratigraphic traps are present, certain contaminants may be locally trapped and thus missed during cleanup operations. Alternatively, if shallow stratigraphic traps are delineated prior to location of cleanup wells, fewer wells may be needed for remediation. For example, a single well located at the trap apex, coupled with a single injection well, might be sufficient if: (1) all contaminants were contained in the trap, and (2) the trap was not laterally extensive. Interfluve stratigraphic traps are formed when braided outwash sands are subsequently covered by backswamp or lacustrine clay deposits. Such traps are common near-surface features of the valley train deposits of the Lower Mississippi River Valley and have relief of a few tens of centimeters to perhaps in excess of 10 m. Interfluve traps are also expected to commonly occur in many glaciated regions. Due to channel migration during backswamp clay deposition, and differing thicknesses of clay cover, it is unlikely that all interfluve traps can be delineated by a single method. Therefore, several geological techniques that might be useful in delineating shallow interfluve traps are briefly discussed here, as well as potential complications in using the described methods. 相似文献
676.
677.
从地球化学角度出发,对钱塘江流域的物质平衡关系及起控制作用的化学风化反应进行了探讨和计算。结果表明,降雨提供了河水中大部分的K~+、Na~+和SO~2-_4。另外,灰岩地区碳酸钙的溶解反应提供了河水中大部分的Ca~2+和HCO~-_3,硅酸盐岩地区钠长石和黑云母生成高岭石的风化反应提供了剩余的K~+、Na~+、H_4SiO_4和大部分的Mg~2+及少量的HCO~-_3。石膏和白云石的风化反应控制了SO~2-_4和Mg~2+的平衡,其中碳酸钙的溶解反应占主导地位。流域的化学侵蚀率和机械剥蚀率分别为0.022和0.071(kg·m-2·a-1),碳酸盐岩区的物质流出量是硅酸盐岩区的2倍。 相似文献
678.
The main characteristics of river flow and grainsize in a bend of the sand bedded meandering river Dommel, The Netherlands, are presented. Measurements were carried out at a relatively low discharge in a sharply curved bend following a long straight reach. In the studied bend, secondary circulation is restricted to the thalweg area; only in the downstream part of the bend it exists over the entire cross-section. Therefore, on the entire pointbar platform, which comprises the larger part of the bend, the median sedimentation diameter of the bedload material is governed by the distribution of the longitudinal components of the bed shear stress only. 相似文献
679.
James E. Pizzuto 《地球表面变化过程与地形》1984,9(3):199-207
Cross-sections of 16 straight sandbed streams in Minnesota, Iowa, and Nebraska were surveyed. Two stratigraphic horizons were found in the banks at each site, an upper cohesive unit usually composed of silt and clay and a lower unit composed of sand. Bank erosion on these rivers occurs when the upper cohesive unit is undercut by scour at bends. The overhanging cohesive block fails by beam or cantilever failure. As upper bank failure is a direct result of undercutting, the stability and rate of retreat of the bank are largely determined by erosion of the sandy part of the bank. The cohesive layer has little influence on bank retreat and width adjustment on the rivers studied here. A quantitative lateral sediment transport model developed by Parker (1978a) is used to calculate the steady-state geometry of the sandy part of the bank. Results are obtained for the shape, length, and height of the sandy part of the bank. The model predicts the length of the bank fairly well, and the theoretical equation for the height of the bank is of the correct form. The model, however, overestimates the slope of the bank. The height of the sandy part of the bank (Db) is approximately equal to the depth of the mean annual flow. Since Db is determined by the lateral sediment transport model, the width (W) may be obtained from the equation of continuity (Q = WDbV), published flow (Q) data, and a resistance equation for the mean velocity, V. The calculated widths are similar to those measured in the field. 相似文献
680.