【摘要】：三峽水庫變動回水末端段河床主要組成物質(zhì)為卵礫石,重慶主城河段是典型的山區(qū)河流彎曲河段,在主城范圍內(nèi)有5個連續(xù)彎道。河床質(zhì)主要是卵石夾砂,河床邊界穩(wěn)定。其礙航特征表現(xiàn)為彎、淺、險。水流、泥沙的共同作用對河床演變的影響較大,卵石灘險的形成機理比較復(fù)雜。長江上游泥沙淤積主要是卵石推移質(zhì)在起作用,卵石推移質(zhì)的輸移帶在消落期可能造成礙航。所以在三峽變動回水區(qū)末端段的航道治理關(guān)鍵技術(shù)中卵石推移質(zhì)輸移帶的寬度和位置的變化顯得尤其重要。本文通過建立1:70的正態(tài)物理河工模型輔以數(shù)學(xué)模型對三峽變動回水區(qū)末端段各典型流量下的水流形態(tài),推移質(zhì)輸移強度,推移質(zhì)輸移帶位置和寬度等特性進行試驗研究。得出變動回水區(qū)末端段各典型灘段的流場,推移質(zhì)輸移帶位置的變化,區(qū)分動沙輸移帶和淤積輸移帶的不同強度的推移質(zhì)輸移方式。對結(jié)果進行大量的統(tǒng)計分析,建立了各灘段推移質(zhì)的不同輸移方式在各級流量下輸移帶強弱分布與流速、水深、比降的變化特性。最后統(tǒng)一成推移質(zhì)輸移帶強弱分布與水流強度指標(biāo)水流功率無量綱數(shù)*W的變化關(guān)系。試驗結(jié)果:三峽變動回水區(qū)末端段各灘險典型流量下的水流流態(tài)分析,推移質(zhì)輸移帶在各灘險的分布特性。輸移帶上*W的變化特性總結(jié)為動沙輸移帶的水流功率普遍比淤積輸移帶的*W值大,可以判斷動沙輸移強度要大于淤積輸移強度,在枯水期和中水期,輸移帶*W明顯要比無輸移帶*W值大。洪水期開始,水面比降下降,輸移帶*W平均值減小。各輸移帶*W值到大洪水期變化區(qū)域穩(wěn)定。結(jié)論:動沙輸移帶的*W值較淤積輸移帶的*W值偏大,說明推移質(zhì)動沙輸移帶是最強輸移方式,淤積輸移次之。中水期輸移帶的*W平均值大約是枯水期*W平均值的2-2.5倍左右,由此可見,在消落期可能出現(xiàn)推移質(zhì)輸移強度減弱造成礙航。洪水期開始,由于水面比降減小的原因,輸移帶的*W值減小,輸移強度減弱,表明在三峽變動回水區(qū)末端會出現(xiàn)蓄水期、汛期淤積,汛末消落期沖刷的推移質(zhì)輸沙特性。對于三峽變動回水區(qū)末端段推移質(zhì)的分布特性進行了總結(jié),區(qū)分了不同的推移質(zhì)輸移強度,對流態(tài)進行了數(shù)值模擬,分析了推移質(zhì)輸移帶強弱分布與水流強度指標(biāo)的變化關(guān)系。在一定程度上,進一步推動了何種水流強度指標(biāo)更適用于在三峽變動回水區(qū)表示泥沙輸移強度的變化。
[Abstract]:The main composition of the river bed in the end of the variable backwater of the three Gorges Reservoir is gravel. The main city of Chongqing is a typical mountain river bend, and there are five continuous bends within the main city. Bed quality is mainly gravel sand, the riverbed boundary is stable. Its obstacle to navigation is characterized by bend, shallowness and danger. The interaction of flow and sediment has a great influence on the evolution of river bed, and the formation mechanism of pebble beach is complex. The sediment deposition in the upper reaches of the Yangtze River is mainly caused by pebble bedload, and the transport zone of pebble bed load may hinder navigation during the falling period. So it is very important to change the width and position of pebble bed load transport zone in the key technology of channel management in the end of the three Gorges variable backwater area. In this paper, the normal physical river engineering model of 1:70 is established, and the characteristics of flow pattern, bed load transport intensity, position and width of bed load transport zone at the end of the three Gorges variable backwater area are studied by means of mathematical model. The flow field and the change of bed load transport zone location in each typical beach section in the end of the variable backwater area are obtained, and the bed load transport modes with different intensity are distinguished between the moving sediment transport zone and the silting transport zone. A great deal of statistical analysis was carried out on the results, and the variation characteristics of the intensity and the velocity, the water depth and the specific drop of the transport zone were established for different transport modes of bed load at different levels of discharge. Finally, the relationship between the intensity distribution of bed load transport zone and the dimensionless power of water flow is unified. The experimental results show that the distribution of bed load transport zone in each beach danger is analyzed under the typical flow at the end of the three Gorges variable backwater area. The variation characteristics of W in the transport belt are summarized as follows: the flow power in the moving sediment transport zone is generally higher than the W value in the silt transport zone, which can be used to judge that the moving sediment transport intensity is greater than the silt transport intensity, and in the dry and middle water periods, The W value of the transport zone is obviously higher than that of the non-transport zone. At the beginning of flood period, the water surface specific drop decreases and the mean value of W in the transport zone decreases. The variation region of W value of each transport belt is stable to the flood period. Conclusion: the W value of the moving sediment transport zone is higher than that of the silt transport zone, which indicates that the bed load moving sediment transport zone is the strongest transport mode, and the silt transport is the second. The average value of W in the transport zone in mid-water period is about 2-2.5 times of that in dry season, so it can be seen that the weakening of bed load transport intensity may result in hindrance to navigation during the period of decline. At the beginning of flood period, due to the decrease of water surface specific drop, the W value of the transport belt decreases and the transport intensity weakens, which indicates that the bed load transport and sediment transport characteristics will occur at the end of the three Gorges variable backwater area during the storage period, the deposition in the flood season and the erosion at the end of the flood period. The characteristics of bed load distribution at the end of the three Gorges variable backwater area are summarized, different bed load transport intensity is distinguished, the convection state is numerically simulated, and the relationship between the intensity distribution of bed load transport zone and the flow intensity index is analyzed. To a certain extent, which water intensity index is more suitable for the variation of sediment transport intensity in the three Gorges variable backwater area.
【學(xué)位授予單位】：重慶交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TV142.2

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本文編號：2213808