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灌区节水改造渠道防渗衬砌形式的探讨 总被引：1，自引：0，他引：1
通过近几年灌区节水改造工程中渠道衬砌的实施,探讨了酒泉市几种有代表性的渠道衬砌形式的运用现状和存在主要问题,并提出了解决途径和措施. 相似文献
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水位流量关系在流域管理中占有十分重要的地位.而对于复式河槽,水位流量关系的推求是十分困难的.无论采用单一河槽法还是传统的断面分割法,都将带来很大的误差.将复式河槽分为滩地边坡区、滩地区、主槽边坡区和主槽区,并运用英国科学工程研究协会洪水水槽设施(SERC-FCF)的大量的系列水槽实验资料,分析了各区Darcy-Weisbach阻力系数之间的关系.SERC-FCF的实验资料表明主槽区的阻力系数与相对水深有关,滩地区和主槽区阻力系数之比随相对水深成指数关系,滩地边坡区、主槽边坡区阻力系数可用主槽区和滩地区阻力系数表示.利用这些阻力系数关系分别推求各区的流量及总流量.实验资料验证表明:计算流量与实测流量基本吻合. 相似文献
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开茂水库区岩溶发育十分复杂,发育程度在空间分布上和规模上具有差异性,在时间上形成多期次岩溶,众多影响岩溶发育的因素相互影响、相互作用。准确、完全地查明库区岩溶现象,几乎不可能,建议在重点处理已经查明的岩溶通道的基础上,预留一定的工作量,待水库蓄水后,根据蓄水后实际情况,在必要情况下进行局部、重点处理。 相似文献
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T. Morales-Juberias P. Zafra M. Olazar I. Antigüedad I. Arrate 《Environmental Geology》1994,24(4):275-280
Carrying out a series of field tracer experiments in river channels allows recognition of river behavior in different flow conditions and thus investigation of the evolution of a solute, tracer, or pollutant over the range of flow rates considered. In this paper, data from tracing tests conducted on the Artibai River in northern Basque Country are used to demonstrate the approach. In all experiments the tracer used was lithium and it was added to the river as an input pulse. An analytical solution to the instantaneous injection model that accounts for the effective initial amount of tracer injected, calculated from the tracer breakthrough curve, instead of the conventional initial injection concentration, is used. The technique is applied to estimate travel times, Péclet numbers, and dispersion coefficients using an optimization algorithm with the aim of characterizing the tracer movement in the stream and analyzing its evolution. Subsequently, considering the results of various tracer experiments, conducted over different flow rates, empirical relationships between dispersion, velocity, and flow rates may be determined. This information allows characterization of the river behavior and can be used to model transportation and dispersion of a tracer or pollutant. 相似文献
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Upward-thickening patterns and lateral continuity of Permian sand-rich turbidite channel fills, Laingsburg Karoo, South Africa 总被引：1，自引：0，他引：1
Martin Grecula Stephen S. Flint Henry De V. Wickens† Stephen D. Johnson‡ 《Sedimentology》2003,50(5):831-853
Abstract Analysis of extensive exposures of the Permian Laingsburg Formation, Karoo basin, South Africa, have enabled a detailed reconstruction of the base of slope stratigraphy and palaeoenvironments in a deep-water system characterized by a very narrow grain-size range (fine sandstone). The deposits include an ≈ 4 km wide and 80 m thick channel complex, fringed by sandy sheet deposits that extend laterally for at least 6 km across depositional strike. Within the channel complex, individual channel fills are marked by shallow basal erosion surfaces draped by thin, parallel-stratified beds of very fine sandstone and siltstone, interpreted as flow tails to largely bypassing flows. These thin beds are overlain by 0·4 to 5 m thick beds of structureless, fine-grained sandstone that represent the majority of the channel fills. The basal packages may be partially to completely removed by localized scour in the axial zone of the channel complex but can be mapped laterally into overbank areas where they thicken and are dominated by rippled fine sandstones with intercalated siltstones. Axial confinement resulted from subtle topography on the basin floor, whereby the lower, dense parts of the initially erosive and bypassing flows were partially confined in the lows and the more dilute, slower moving upper parts of the flows deposited sheet-like successions across slightly elevated overbank areas. The narrow grain-size distribution prohibited the formation ofcoarse-grained residual bypass deposits during the initial phases of channel formation. With decreasing magnitude, later flows became more depositional, filling remaining axial depressions with thick-bedded structureless sandstone. The smaller volumes of late-stage sediment were more axially focused, producing local scour-and-fill features and starvation of the overbank areas. Resulting grain-size vertical profiles are complex. The basal flow tail packages and overlying massive deposits form a thickening and slightly coarsening-upward trend in the channel fills. The overbank deposits show a thinning- and fining-upward profile as a result of less bypass plus late-stage starvation of sand. Application of traditional deep-water facies models could therefore potentially lead to erroneous interpretations of the channel complex as a prograding lobe and the overbank sheets as channel-fills. 相似文献
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Glacial meltwater channels are incised into bedrock and diamicton along much of the length of the Mid-Cheshire Ridge. Detailed mapping of one such system near the town of Helsby reveals a dendritic channel network developed in the opposite direction to the regional ice flow during the last (Late Devensian) glaciation. The channels formed subglacially, under atmospheric and not hydrostatic pressure, presumably as the ice sheet downwasted during deglaciation. Morphological and palaeohydraulic evidence suggests that not all of the network was necessarily active contemporaneously. Former water levels in the channels can be estimated due to the presence of bar surfaces, giving a calculated palaeodischarge of at least 111 m3 s−1. The ablation rates required to account for this large discharge are an order of magnitude greater than those obtained from theoretical calculations and those observed in modern glacial environments. This implies that some form of high-magnitude discharge, such as a seasonal flood event, must have taken place in this area during deglaciation. This picture of the Late Devensian ice sheet suggests that during recession the ice sheet was static, crevassed and relatively thin (<50 m). This study also shows that there is no simple relationship between meltwater channel direction and ice dynamics, and that care is required when using the former to make inferences about the latter. Copyright © 1998 John Wiley & Sons, Ltd. 相似文献
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The bedrock surface of many glaciated areas is obscured by thick drift deposits. In southern Ontario, Canada, the buried bedrock surface is dissected by channels, infilled with glacial deposits as much as 150 m thick, that are part of a wider mid-continent preglacial fluvial system that predates formation of the modern Great Lake basins. The infills of bedrock channels form major groundwater aquifers, influence regional groundwater flows and contaminant migration to Lake Ontario, and may localize the release of thermogenic methane and radon within heavily urbanized surface environments. A quantitative comparison of the regional pattern of bedrock joints and the orientation pattern of buried bedrock channels and modern river valleys shows that all these orientation patterns are virtually coincident. Buried bedrock channels in south-central Ontario are not part of a simple antecedent drainage system but were likely predesigned by bedrock joint patterns that have subsequently been propagated upward into overlying Pleistocene sediments. Joints in sediments are of considerable environmental significance (for example, subsurface contaminant and gas migration in fine-grained clayey sediments) and of many origins (stress release, desiccation, etc.) but are widely assumed to be a predominantly surface-related phenomena; the existence of deeper joints has been noted by some authors but their origin is obscure. Data presented herein from south-central Ontario confirm that, in addition to surface-related joints, a second population of bedrock-related joints, reflecting the upward propagation of bedrock fractures, is present in Pleistocene sediments of south-central Ontario. 相似文献
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不同流量级下,分汊河段进口主流摆动导致江心洲头部的平面冲淤分布呈现出复杂变化特征。为探究江心洲头部冲淤与来流过程之间的响应关系,借助长江中下游多个分汊河段内水沙、地形资料,对江心洲头部水动力特征实施了数值模拟,并对不同流量级下的河床变形强度进行综合比较。研究表明:江心洲头部低滩的冲淤动力随着流量涨落呈现出明显的临界特性,冲淤过程中存在大、小两个临界流量Q1与Q2,在介于两个临界流量之间的流量级持续作用下,洲头低滩发生冲刷;流量大于Q1或小于Q2时,洲头低滩表现为淤积。由于不同流量级造成的冲淤效果不同,因而水文过程中各级流量的持续时间,是影响洲头低滩年内、年际变形的主要因素。 相似文献
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阐述了煤炭地质档案信息资源的管理应用现状及未被充分利用的原因；地质档案在生产科研中起到了不可替代的作用。提出了如何发挥煤炭地质档案的作用和充分利用档案资源的途径。 相似文献
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Submarine canyons are conduits for the distribution of sediment across continental margins. Although many canyons connect directly with fluvial or marine littoral system feeders, canyons detached from direct hinterland supply are also recognized. The fill of detached canyons remains enigmatic, because their deep‐water setting restricts analysis of their evolution and stratigraphic architecture. Therefore, this study aims to investigate the sedimentary processes that infilled deep‐water canyons and the resulting architecture. Miocene outcrops of an exhumed deep‐water system from the East Coast Basin, New Zealand, are documented and compared with the morphology and seismic scale architecture of a modern detached canyon system on the same convergent margin. The outcropping system preserves the downstream margin of a sub‐basin deposited at palaeo‐water depths >700 m. A 6 km wide by 430 m deep incision is filled by heterogeneous siliciclastic sediments, 50% of which comprise graded thin‐beds with traction structures, interpreted to result from oscillatory flows. These are intercalated with concave‐up lenses, up to 15 m thick, of sigmoidally‐bedded, amalgamated sandstones, which preserve ripple casts on bed bases, interpreted as deposits at the head of a deep‐marine canyon. Palaeo‐flow was eastward, into the sub‐basin margin. On the adjacent margin of the sub‐basin down‐dip, stacked and amalgamated sandstones and conglomerates represent the fill of a submarine channel complex, at least 3 km wide. The channels are inferred to have been fed by the up‐dip canyon, which traversed the intervening structural high; similar relationships are seen in the bathymetry data. Seismic studies on this margin demonstrate that multiple phases of canyon cut and fill may occur, with downstream architectural evolution comparable to that seen at outcrop, demonstrating that detached canyons may act as sediment conduits. Breaching of developing sea‐floor structures by detached canyons can modify tortuous sediment pathways, supplying sediment to otherwise starved areas of the slope. 相似文献
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Turbidites in the Upper Carboniferous Ross Formation, western Ireland: reconstruction of a channel and spillover system 总被引：2，自引：0，他引：2
ABSTRACT The Upper Carboniferous deep‐water rocks of the Shannon Group were deposited in the extensional Shannon Basin of County Clare in western Ireland and are superbly exposed in sea cliffs along the Shannon estuary. Carboniferous limestone floors the basin, and the basin‐fill succession begins with the deep‐water Clare Shales. These shales are overlain by various turbidite facies of the Ross Formation (460 m thick). The type of turbidite system, scale of turbidite sandstone bodies and the overall character of the stratigraphic succession make the Ross Formation well suited as an analogue for sand‐rich turbidite plays in passive margin basins around the world. The lower 170 m of the Ross Formation contains tabular turbidites with no channels, with an overall tendency to become sandier upwards, although there are no small‐scale thickening‐ or thinning‐upward successions. The upper 290 m of the Ross Formation consists of turbidites, commonly arranged in thickening‐upward packages, and amalgamated turbidites that form channel fills that are individually up to 10 m thick. A few of the upper Ross channels have an initial lateral accretion phase with interbedded sandstone and mudstone deposits and a subsequent vertical aggradation phase with thick‐bedded amalgamated turbidites. This paper proposes that, as the channels filled, more and more turbidites spilled further and further overbank. Superb outcrops show that thickening‐upward packages developed when channels initially spilled muds and thin‐bedded turbidites up to 1 km overbank, followed by thick‐bedded amalgamated turbidites that spilled close to the channel margins. The palaeocurrent directions associated with the amalgamated channel fills suggest a low channel sinuosity. Stacks of channels and spillover packages 25–40 m thick may show significant palaeocurrent variability at the same stratigraphic interval but at different locations. This suggests that individual channels and spillover packages were stacked into channel‐spillover belts, and that the belts also followed a sinuous pattern. Reservoir elements of the Ross system include tabular turbidites, channel‐fill deposits, thickening‐upward packages that formed as spillover lobes and, on a larger scale, sinuous channel belts 2·5–5 km wide. The edges of the belts can be roughly defined where well‐packaged spillover deposits pass laterally into muddier, poorly packaged tabular turbidites. The low‐sinuosity channel belts are interpreted to pass downstream into unchannellized tabular turbidites, equivalent to lower Ross Formation facies. 相似文献
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利用较高分辨率的遥感影像确定出古居延绿洲渠系分布和引水口的位置以及古渠道线路的走向,发现古居延绿洲主要分布在现代绿洲的东侧,至少有6处引水口分布于距雅布赖、东城圈和马圈城一线西侧的水道上。渠系由西向东进入各垦区,各引水口随水道西迁向西延伸。渠系与遗址、古耕地和红柳包间的联系以及14C\}测年数据表明： 多数渠系始建于汉代,以后长期延用,盛于西夏,弃于元末明初; 古居延绿洲早期荒漠化始于1300aB.P.; 天然水系向西迁移最终导致了古居延绿洲的废弃和完全荒漠化 相似文献
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为了探索宽窄相间河道的水流紊动特性,以西南地区宝兴河上游宽窄相间河段为研究对象,基于室内概化模型试验,采用多普勒声学流速仪(ADV)测量了室内模型典型断面上的三维瞬时流速,分析典型断面上的纵向时均流速、紊动强度、雷诺切应力和紊动能的分布规律。试验结果显示:宽窄相间水槽中,扩散段边壁的紊动强度大于中心区域的紊动强度,最大值位于0.2倍水深处;扩散段两侧坡脚处紊动能最大;侧壁区的平面和立面雷诺切应力最大值出现在扩散段内,中心区域最大雷诺切应力位于两槽间的中间断面处;扩散段内水流紊乱,两侧出现旋涡和涡脱,易造成侧壁侵蚀加强,引起河道拓宽。深入分析了宽窄相间河道水流的紊动特性,可为山区河流治理和自然灾害防治提供参考。 相似文献
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Detailed fieldwork and new extensive 14C dating of residual channel infillings provide data for the reconstruction of the Late‐glacial channel downcutting and incision history of the Venlo–Boxmeer lower reach of the River Meuse (= Maas) in the southern Netherlands. Within a period of 500–1300 yr after Late‐glacial climatic amelioration, the Meuse responded to increased discharges and decreased sediment supply by adjusting the width/depth ratio of its channels. Two main phases of channel downcutting are followed by two main phases of floodplain lowering and narrowing, indicating net floodplain degradation by the fluvial system as a non‐linear response to Late‐glacial and Early Holocene climate change. Some 1300 yr after initial late‐glacial warming, channels downcut rapidly during the Early Bølling (13.3–12.5 kyr BP) and adopted a high‐sinuosity meandering style. Channel downcutting paused around 11.9 kyr BP, possibly in response to rising groundwater levels and/or the Older Dryas cooling event. Between 11.9 and 11.3 kyr BP a new floodplain was formed. Then, lateral erosion took place and initiated a first phase of 2.6 m floodplain lowering during the Late Allerød. Gradual climate deterioration during the Allerød progressively broke up soils and vegetation cover, from 11.3 to 10.9 kyr BP. The Meuse gradually adjusted to an increased ratio of sediment supply over transport capacity through higher width/depth ratios. Main channels became shallower and adopted a low‐sinuosity pattern, finally culminating in a braided river system during the Younger Dryas. The final Holocene warming resulted, within 500 yr, in renewed rapid channel downcutting by a single low‐sinuosity channel during the Early Preboreal, followed by a second phase of 1.8–2.8 m floodplain lowering. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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为了探索宽窄相间河道的水流紊动特性，以西南地区宝兴河上游宽窄相间河段为研究对象，基于室内概化模型试验，采用多普勒声学流速仪（ADV）测量了室内模型典型断面上的三维瞬时流速，分析典型断面上的纵向时均流速、紊动强度、雷诺切应力和紊动能的分布规律。试验结果显示：宽窄相间水槽中，扩散段边壁的紊动强度大于中心区域的紊动强度，最大值位于0.2倍水深处；扩散段两侧坡脚处紊动能最大；侧壁区的平面和立面雷诺切应力最大值出现在扩散段内，中心区域最大雷诺切应力位于两槽间的中间断面处；扩散段内水流紊乱，两侧出现旋涡和涡脱，易造成侧壁侵蚀加强，引起河道拓宽。深入分析了宽窄相间河道水流的紊动特性，可为山区河流治理和自然灾害防治提供参考。 相似文献
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南洞地下河岩溶管道展布及结构特征的示踪试验解析 总被引：7，自引：6，他引：1
运用高精度的示踪试验研究了南洞地下河流域部分岩溶管道的展布状况,并对暗河管道的结构特征进行了分析。试验结果表明:一号暗河有一独立的含水系统,补给区为瓦白白一带,二号暗河主管道总体通往永宁和石洞方向,三号暗河通往城红寨方向,二号暗河和三号暗河在南洞口附近有连通,枯季时二号暗河补给三号暗河。此外,一号暗河和二号暗河分别呈老年期和壮年期地下河形态,较为畅通;三号暗河则发育较晚,出口处有较多的裂隙。最后,结合现有的资料及流域内的水文地质条件,对流域内岩溶管道的大体分布位置进行了推断,绘制了岩溶管道的展布图,以期为南洞地下河流域的岩溶水文地质调查、物探、钻探及地下水开发利用等提供理论依据。 相似文献