长江口青草沙水库前沿河床动力地貌过程及库堤安全预警分析

发布时间：2017-12-28 01:21

本文关键词：长江口青草沙水库前沿河床动力地貌过程及库堤安全预警分析　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：河口位居陆海交汇的狭窄区域,因其拥有自然和人类无与伦比的资源(如生物多样性、航道)而对全球和局部区域的发展具有重要价值。高强度人类活动作用下的河口动力地貌过程一直是当前国际陆海相互作用计划以及未来海岸计划研究的重点内容。然而,随着近年来水利工程建设的开展,上游来水来沙条件发生改变,进入下游河道的能量分配和泥沙输移量随之转移,河口区的地貌自然格局已有较大变化,这已成为科学和社会不同层面面临的共同挑战。青草沙水库作为长江河口区近年来最大的水利工程之一,不仅是上海市最大的城市供水水源地,也是国内迄今为止规模最大的避咸蓄淡型河口江心水库。水库位于上接南支河道,下控南北港河势的南北港分流口附近,周围暗沙罗列,变动频繁,河势复杂多变,演变趋势不明朗,这将影响青草沙水库前沿岸堤的稳定与上海市饮用水的供给安全。因此开展库区前沿河床动力地貌过程对青草沙水库工程响应的研究,具有重要的理论和应用价值。本文基于2006-2015年长江口北港实测水文泥沙资料(主要包括流速、流向、含沙量、悬沙底沙级配等数据)分析青草沙水库前沿河段水动力和悬沙分布等特征。利用长江口南北港分流口区域采集的2000、2002、2004、2007以及2009-2013等多年实测水深资料,诊断青草沙水库前沿滩槽形态的变化和稳定性特征,进而探讨水库前沿的河床冲淤变化过程。主要结论包括:从水流特性来看,北港分流口水流运动形式主要为往复流,以落潮流占优势。其中落潮历时大于涨潮历时,落潮流速大于涨潮流速。枯季涨潮动力强于洪季,落潮动力弱于洪季。研究区域水体含沙量分布表现为落潮大于涨潮,枯季全潮含沙量大于洪季。其中水体的含沙量沿垂线分布是由底部向表层递减;在憩流时段附近,垂线流速紊乱、含沙量沿垂线分布展现无明显变化的分布特征。同时,涨、落急时段内流速大、水流动力和挟沙能力强、含沙量大;憩流时段内水流速度小、含沙量相对较小。新桥通道附近含沙量低于青草沙水库尾闾所在位置。从悬沙粒径沿程分布来看,北港分流口河段表现为:新桥通道附近颗粒较粗,青草沙水库尾闾所处位置颗粒较细。表层沉积物颗粒组成表现为南北港分流口河段河床表层沉积物较粗,主要有细砂和砂两种主要类型,分选性较好;北港青草水库前沿主槽河段河床表层沉积物颗粒组成较细、分布有细砂和粉砂质砂两种类型、分选性相对较好,这在一定程度反映了北港主槽水动力略弱于南北港分流口。研究区河床冲淤表现为:库堤前沿河床出现上部先冲再淤,中下部由强到弱的淤积过程。水库库堤前沿边滩以及堡镇沙尾部位是重点淤积区域,北港主槽淤积不明显。青草沙水库前沿河床冲淤变化在水库建设前后有明显差异:建库前总体表现为河槽冲刷、沙洲淤积,呈现准冲-淤振荡性质;建库后表现为持续冲刷。水库库堤前沿河床也由之前的周期性冲-淤变化转为幅度逐渐减弱的持续冲刷。同时,水库前沿河床的沙体沿落潮主流方向移动,成形沙体先增长、再减少,最后趋于平衡,隐形沙体主要分布在南北港分流口以及水库库堤前沿,堡镇沙附近有少量分布。此外,青草沙水库前沿河床河槽形态由U型向U型和V型河槽叠加的复式河槽转变。其中上部河床边滩刷深、中部河床l栍倨胶狻⑾虏亢哟睻型槽上叠加V型复式河槽。青草沙水库库堤前沿不到600 m位置是河床失稳的重点风险区域,尤其是水库库堤中上部河床处于不稳定状态,如前沿边坡所在河槽进一步逼近水库前沿,则河床面临进一步冲刷的可能。
[Abstract]:The estuary is located in the narrow area where land and sea converge. Because it has natural and human resources, such as biodiversity and waterway, it is of great value to the development of global and local regions. The dynamic geomorphologic process of estuaries under the action of high intensity human activities has been the focus of current international land sea interaction plan and future coastal planning research. However, with the development of water conservancy construction in recent years, the upstream runoff and sediment conditions change, energy distribution and sediment transport into the downstream channel shifted, natural geomorphic patterns have great changes in the estuary, which has become the common challenges facing different levels of science and society. The grass sand reservoir in the Yangtze River Estuary as one of the largest water conservancy project in recent years, not only is the largest city of Shanghai water supply, is by far the country's largest freshwater storage to avoid salty type River Estuary reservoir. The reservoir is located in the South Branch of the river on the ground, under the control of the north and south south and North River distributary shoal near the mouth, around the list changes frequently, terrain complex, the evolution trend of uncertainty, which will affect the stability of drinking water in Shanghai coastal levee Qingcaosha Reservoir before the supply of security. Therefore, it is of great theoretical and practical value to carry out the research on the response of the river bed dynamic geomorphology to the engineering response of the green grass and sand reservoir. In this paper, 2006-2015 north channel of Changjiang Estuary hydrology based on sediment data (including velocity and sediment concentration, suspended sediment gradation data such as Sha DI) of Qingcaosha Reservoir before the water along the river hydrodynamic and sediment distribution characteristics. The port in the South and North diversion regional collection of 2000, 2002, 2004, 2007 and 2009-2013 years of measured bathymetric data, diagnosis of Qingcaosha Reservoir variation before the groove shape and stability characteristics of Yantan reservoir, and then discusses the frontier of riverbed erosion process. The main conclusions are as follows: from the flow characteristics, North diversion flow slobber is mainly in the form of reciprocating flow, with the ebb dominant. The ebb duration is longer than that of the flood and ebb tide flow rate is greater than. The dry season power Yuhong season, tide power weak Yu season. Study on regional water sediment concentration distribution is greater than the ebb tide, the dry season Quanchao sediment concentration is greater than the flood season. The sediment water distribution along the vertical direction is decreasing from the bottom to the surface; in the slack period near the vertical velocity, sediment concentration distribution along the disorder showed no significant changes in the vertical distribution. At the same time, the rise and fall of acute period of high velocity, hydrodynamic and sediment carrying capacity, large sediment; slack period flow velocity and sediment concentration relatively small. Xinqiao channel near the sediment below the grass sand reservoir at the location. The grain size distribution, the North River diversion performance: the bridge channel near the coarse particles, Qingcaosha Reservoir located in fine particle at. The surface sediment particle composition showed the north port diversion of river bed surface sediment is thick, there are two types of fine sand and sand, good sorting; North grass reservoir riverbed sediments front main component is small, the distribution of fine sand and silty sand, two types of sorting is relatively good, this to a certain extent reflects the main channel of the north channel hydrodynamic slightly weaker than the South and North diversion. The scouring and silting of riverbed in the study area shows that the upper part of the riverbed is first washed and re silted in the upper part of the bank, and the middle and lower part of the river bed is from strong to weak. The reservoir dike beach front and tail parts is the focus of Bao Zhen Sha siltation area, sediment deposition is not obvious. Qingcaosha Reservoir frontier of riverbed erosion have obvious differences in the reservoir before and after the construction: before the construction of the overall performance of channel erosion and sand deposition, a quasi - and impulse oscillation properties; after the reservoir showed continued erosion. The river bed in front of the reservoir bank also changed from the previous periodic flushing and silting to the gradual weakening of the scour. At the same time, the mobile sand reservoir before the river bed along the mainstream direction, forming the first sand body growth, then decreases, finally tends to balance the distribution of sand body in the South and north main contact and reservoir diversion dike frontier, a small amount of the distribution of sand near the town. In addition, the grass sand reservoir before stacking along the bed channel morphology from U type to U type and V type channel double channel transformation. The upper river beach, Central River l deep brush glue, Lu Kang Suan from Xuan yo groove superimposed on the V type compound channel. Qingcaosha Reservoir dike frontier less than 600 m position is the focus of risk loss of riverbed area stability, especially the reservoir in the upper river embankment is in an unstable state, such as the slope where the channel further approaching the reservoir frontier, is facing further erosion of riverbed may.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV143;TV698

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