近期长江河口典型河槽动力沉积地貌过程

发布时间：2018-03-25 02:38

本文选题：长江河口　切入点：潮动力　出处：《华东师范大学》2015年硕士论文

【摘要】：近年来随着水土保持工程、三峡工程和南水北调工程等长江流域大型工程的建设,将会使流域来水来沙及其季节分配发生明显变化；而长江口大规模促淤围垦、深水航道、南汇人半工岛、大型水库、跨江和跨海大桥等河口工程的兴建又将改变河槽的边界条件,从而使各汉道的分流比发生改变,进而会改变潮流流速的大小和方向、悬沙的时空分布、沉降及输运,继而导致河槽地貌发生变化,河槽地貌的改变又会影响潮动力和悬沙浓度的变化。而当潮动力、悬沙浓度及地貌发生变化后,将会对河槽边界的稳定性及河口大型工程的安全性产生较大影响,因而是一个直接涉及到河口工程、航道运输以及沿岸人民生命财产的安全问题。基于以上因素,本文在前人的研究基础之上,以长江河口北港上段、北槽中上段,南汇南滩水域为研究对象,利用近年来在长江河口现场实测潮流、悬沙、地貌资料以及相关潮位站的潮位资料,研究近期长江河口河槽动力沉积地貌变化过程和水沙输运机制,并探讨动力沉积地貌变化过程对大型工程的响应机制。这将有助于深入了解近期河口河槽的动力沉积地貌过程,为合理开发利用河口和近海资源提供理论基础,并为河口工程维护、航道疏浚及河槽治理提供参考依据。因此,本文的研究具有重要的理论和实践意义。主要研究结果如下：1.潮汐变化过程。近期研究区域内潮汐性质均为非正规半日浅海分潮,潮动力的非线性特征更加明显；北港上段、北槽上段河槽浅水分潮性质加强,北槽中段、南汇南滩水域浅水分潮性质变化不明显。2.潮流变化过程。北港上段河槽2003-2007年流速减小0.19-0.28 m/s,落潮优势洪季减弱、枯季增强；2007-2012年流速洪季增大、枯季减小,落潮优势洪季增强、枯季减弱。深水航道三期工程后,北槽中段河槽南侧流速略减,落潮优势稍减弱。2003-2012年南汇南滩水域流速洪季增大、枯季减小,落潮优势洪季增强、枯季减弱。3.悬沙浓度变化过程。北港上段2003-2007年悬沙浓度约减少0.10 kg/m3,优势沙洪季减小、枯季增大：2007-2012年悬沙浓度洪季减少、枯季增多,优势沙洪季增大、枯季减小。深水航道三期工程后,北槽中段河槽南侧悬沙浓度增多0.31-0.48 kg/m3,洪季优势沙增大。2003-2012年南汇南滩水域悬沙浓度减少0.19-1.11kg/m3,优势沙洪季增大、枯季减少。4.洪、枯季床面微地貌特征。北港上段洪(2014年7、10月)、枯(2015年2月)季微地貌形态变化明显,洪季比枯季沙波发育范围广。新桥通道内洪季多为复合沙波,枯季变成单一沙波。横沙通道北口水域洪季发育有弯曲型和顺直型两种类型的沙波；枯季弯曲型沙波发育区沙波消失且发育着许多椭圆形的麻坑,顺直型沙波波长变大。洪、枯季河床微地貌的异同主要与洪、枯季期间水动力条件以及沉积物的粒径和分选性有关。5.近期浅层沉积结构变化过程。2010年1月至2014年10月北港上段新桥通道内浅地层剖面表层形态及分层结构变化不明显,且均为单层分层、厚度约2m。在北港上段横断面最窄附近,2014年10月断面开始大幅度冲刷并向下游持续的距离较长,最大刷深约为7 m。2010年1月至2014年10月北港上段长江大桥以西剖面结构变化显著,上游分层由双层变为单层,中间分层消失,下游部分分层变厚、部分分层由双层变为单层。6.水沙输运机制。悬沙纵向输运的主要驱动力包括欧拉余流(向海)、潮泵效应、垂向环流(向陆)和斯托克斯余流(向陆),欧拉余流在平流输沙中占主导地位,潮泵效应在潮流输沙中占主导地位,潮泵效应除北港、南槽口外随季节变化外其余河槽均指向海。徐六泾悬沙主要由欧拉余流向海输运,南支北侧主要由欧拉余流和潮泵效应均向海输运,北港上段、南港中段主要由欧拉余流、潮泵效应向海和垂向环流向陆输运,北支中上段、北港中下段、北槽中段、南槽南边滩主要由欧拉余流、潮泵效应向海和斯托克斯余流、垂向环流向陆输运,口外主要由欧拉余流向海和垂向环流向陆输运。7.近期动力沉积地貌过程对大型工程的响应机制。青草沙水库建成后使北港上段河槽缩窄、断面束水、水动力增强,再加上流域来沙减少致使悬沙浓度减少,水流会带起河槽底部泥沙,从而导致北港上段河槽发生冲刷。深水航道三期工程南导堤加高的阻流作用、泥沙再悬浮和上游来水来沙使中段悬沙浓度增大以及上段潮动力的非线性特征增加强于中段是致使北槽中段河槽淤积的主要原因。上游来沙量的减少、南汇边滩附近促淤围垦工程的建设以及沙体的迁移使得该水域悬沙浓度减少,促淤围垦工程和东海大桥的建设使得该水域洪季潮流流速增大、枯季涨潮流优势加强；潮动力增强和悬沙浓度减少进而导致南汇南滩水域河床冲刷明显。可见,河口河槽动力沉积地貌过程不但与流域来沙有关,还与河口局部工程建造存在着直接联系。
[Abstract]:In recent years, along with the soil and water conservation project, the construction of the Three Gorges Project and the South North diversion project and other large projects in Yangtze River Basin, will make the runoff from the basin and its seasonal distribution changed significantly; and the mouth of the Yangtze River siltation reclamation large-scale, deepwater channel, Nanhui half Island, large water pool, cross river bridge and other estuarine engineering the building will change the channel boundary conditions, so that the Chinese road diversion ratio changed, thus changing the magnitude and direction of flow velocity, the temporal and spatial distribution of suspended sediment, sedimentation and transport, and then lead to the change of channel geomorphology, channel changing landscape will affect tidal power and suspended sediment concentration change. When the concentration of suspended sediment in tidal power, and topography changes, have a greater impact on the stability and security will channel boundary and large-scale estuarine engineering, which is a directly related to estuarine engineering, waterway transport The security problem and lose the people's life and property along. Based on the above factors, on the basis of previous research, in the Yangtze River Estuary in the upper, upper North trough and South Beach Nanhui waters as the research object, in recent years the use of suspended sediment in the Changjiang Estuary, tidal field, landform data and tidal data related to tidal station. A recent study in the Yangtze Estuary Channel sedimentary geomorphic processes and sediment transport mechanism, and explore the response mechanism of sedimentary geomorphic processes of large power engineering. It will have dynamic sedimentary processes helps to further understand the recent estuarine channel, to provide a theoretical basis for the rational development and utilization of estuarine and coastal resources, and estuarine engineering maintenance and to provide reference for dredging and channel management. Therefore, it has important theoretical and practical significance of the research in this paper. The main results are as follows: 1. tidal changes Cheng. Recent tidal characteristics in the study area are non regular semidiurnal tidal shallow, nonlinear characteristics of tidal power is more obvious; the upper North, North trough of upper channel shallow water tide properties strengthened, middle section of the north passage, Nanhui south beach waters, shallow water tide properties change process is not obvious. The upper channel North.2. trend 2003-2007 years the velocity 0.19-0.28 m/s, ebb flood season weakened, dry season flow enhancement; 2007-2012 years flood season increased, dry season reduced ebb flood season increased, dry season decreased. The deepwater channel project phase three, speed slightly reduced North trough of middle south part of the river channel flow, ebb weakened slightly.2003-2012 Nanhui south beach waters flow the flood season increased, dry season reduced ebb flood season increased, dry season decreased.3. suspended sediment concentration change process. In upper 2003-2007 years suspended sediment concentration decreased about 0.10 kg/m3, the advantage of the flood season sediment decreases, dry season increase: 2007-2012 The concentration of suspended sediment in the flood season year reduced dry season increased, dominant sediment in flood season increased, dry season decreased. The deepwater channel project phase three, middle section of the north passage channel on the south side of the suspended sediment concentration increased 0.31-0.48 kg/m3, flood season increased.2003-2012 dominant sediment of Nanhui south beach waters, suspended sediment concentration reduced 0.19-1.11kg/ m3, dominant sediment in flood season increased dry season, dry season reduced.4. flood bed surface micro landform. On the north section of the flood (2014 7,10 months), dry season (February 2015) micro topography changes obviously, the flood season than in dry season. The dune development range of Xinqiao channel flood season for composite sand, dry season has become a single sand. Bending straight type and two types of sand North waters of Hengsha passage in flood season development; dry season bend dune development sand waves disappeared and many developed oval pits, straight Sandwaves wavelength becomes larger. The dry season river flood, similarities and differences between the micro topography and the main flood during the dry season. Hydrodynamic conditions and sediment particle size of about.5. and the sorting of the recent changes in the shallow sedimentary structure of.2010 from January to October 2014 in the upper bridge channel change profile of the surface morphology and hierarchical structure of shallow strata is not obvious, and is the single layered, the thickness is about 2M. in the north near the upper cross section of the narrow section, October 2014 began to greatly scour and downstream continuous long distance, the maximum scour depth is about 7 m.2010 from January to October 2014 in the upper Yangtze River bridge west section structure changed significantly, stratified by double into upstream monolayer, the middle layer disappeared, the downstream part of layered thick, partially layered by double into water and sediment transport mechanism of.6. single main driving. The force of suspended sediment transport including longitudinal Eulerian flow (Xiang Hai), tidal pumping effect, vertical circulation (landward) and Stokes (Xiang Lu), the residual current flowing in the Eulerian advection for sand The dominant position, the tidal pumping effect in tidal sand dominated tidal pumping effect in North, south of the groove opening varies with the season the river channel are pointing to the sea. Xu Jing six suspended sediment is mainly composed of Euler residual flow to sea transport, on the north side of South Branch is mainly composed of Euler residual current and tidal pumping effect to the sea transport, north south middle upper, mainly by the Euler residual current and tidal pumping effect to vertical circulation to the sea and land transport, upper North Branch, north middle section, middle section of the north passage, South South Beach trough is mainly composed of Euler residual current and tidal pumping effect to the sea and the Stokes residual current, the vertical circulation to land transport, mainly by extraoral Euler residual flow to the sea to the land circulation and vertical transport of.7. recently sedimentary geomorphic process response mechanism of the large-scale project. Built in Qingcaosha Reservoir after the upper north channel narrow beam section water, water power increased, coupled with the decrease in riverine sediment in suspended sediment concentration reduce water. Bring up the channel flow of sediment at the bottom, resulting in north channel erosion. The upper stage three deep waterway project south dike heightening the flow resistance, sediment resuspension and sediment from the upstream to the middle of suspended sediment concentration increased and the nonlinear characteristics of upper tidal power increased in the middle is the main reason causing strong middle section of the north passage and the siltation.. reducing the upstream sediment, Nanhui beach near and promoting the construction of the reclaiming project and migration of sand makes the waters of the suspended sediment concentration is reduced, the construction of siltation reclamation project and the East China Sea Bridge makes the waters of the flood season tide velocity increases, the dry season tide advantage strengthened; tidal power enhancement and suspended sediment concentration to reduce the resulting Nanhui south beach waters scour significantly. Therefore, channel power estuary sedimentary processes not only with sediment, and local estuary construction there is a direct relationship.

【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TV148

【相似文献】