小型水坝拆除后沉积物侵蚀沉积规律及局部河貌变化
发布时间：2018-10-15 20:49
【摘要】：水库大坝具有防洪发电、灌溉供水、航运旅游等多种功能,我国已建有水坝约9.8万座,多为小型水坝。受当时技术、经济等的制约,很多水坝在规划、设计、施工和管理等方面存在一定欠缺,随着使用寿命的临近,其安全、经济和环境等方面的负面效应日益突出。针对一些安全性差、功能丧失严重、生态环境影响恶劣的小型水坝,实施降等或报废拆除是一种必要管理措施。相对于水坝建设运行,其报废拆除将再次打破河流的生态平衡,引起河流水动力和泥沙的剧烈变化,同时间接对河流生物栖息地产生影响。目前,拆坝后库区及坝下河道泥沙情势短期内急剧变化及其长期生态河貌影响已成为拆坝工程的巨大挑战,研究拆坝后水动力泥沙情势变化过程及其地貌响应具有重要意义,将为水坝报废拆除提供理论参考和技术支撑。本文利用贵州省西河大坝拆除案例,通过实测地形数据和泥沙基本资料,推算了西河无资料流域降雨径流过程和含沙量,利用Delft3D建立西河二维水沙模型,分别模拟了拆坝前库区长期泥沙淤积情况、拆坝后河道短期和长期的水动力与泥沙变化以及河貌演变,同时研究了不同拆坝方式对库区泥沙运动和地貌变化的影响,得到以下结论:(1)对于无资料地区小型河流,在对临近水文站长序列数据分析后,利用水文比拟法和降水径流频率相应法推算得到的西河年径流均值相一致,符合地区分布规律及下垫面特点。(2)通过模拟建坝后的水沙运动过程,表明大坝修建使大量泥沙在库区淤积,其淤积形态为“锥形淤积”;坝后由于下泄流量变小河道整体流速降低。(3)通过模拟拆坝后短期和长期的水沙过程,表明拆坝后短期内,由于水库瞬时大量排水,坝上坝下高水头差使坝址流速很大,导致库区泥沙发生下切侵蚀,主河道冲刷非常严重,产生裂点向上游迁移,侵蚀上游更多的泥沙;主河道两侧由于水位迅速下降导致两侧高程较大的地方流速小而发生淤积;下游因水量下泄流速太大泥沙基本不会淤积。长期来看,经过枯水期和平水期泥沙冲淤变化不大,但经过洪水期后大量泥沙向下游输运同时落淤在河道两侧;河道形态在上游变化剧烈,向窄深方向发展,下游变化不太显著。(4)分阶段拆坝和一次性拆坝相比,减小了坝上坝下水头差,形成的正向与负向波都较小,流速相对较低,侵蚀不够严重,溯源侵蚀距离较短,但长期来看,泥沙冲淤分布和一次性拆除类似。
[Abstract]:Reservoir dams have many functions, such as flood control and power generation, irrigation and water supply, shipping and tourism. There are about 98000 dams in China, most of which are small ones. Restricted by technology and economy at that time, many dams are deficient in planning, design, construction and management. With the approaching of service life, the negative effects of safety, economy and environment are becoming more and more prominent. For some small dams with poor safety, serious loss of function and bad ecological environment, it is a necessary management measure to carry out downgrade or scrap demolition. Compared with dam construction and operation, its scrapping and dismantling will once again upset the ecological balance of the river, cause dramatic changes in river hydrodynamic force and sediment, and indirectly affect the biological habitat of the river. At present, the rapid change of sediment situation in the reservoir area and the river channel under the dam after dam removal and its long-term ecological river profile have become a great challenge for the dam demolition project. It is of great significance to study the variation process of hydrodynamic sediment situation and its geomorphological response after dam removal. It will provide theoretical reference and technical support for dam scrapping and demolition. Based on the case of Xihe dam demolition in Guizhou Province, the process of rainfall runoff and sediment content in Xihe River basin without data are calculated through the measured topographic data and basic sediment data. A two-dimensional model of water and sediment in Xihe River is established by using Delft3D. The long-term siltation of the reservoir area before the dam removal, the short-term and long-term hydrodynamic and sediment changes of the river after the dam removal and the evolution of the river profile are simulated, respectively. At the same time, the effects of different ways of removing the dam on the sediment movement and geomorphologic change in the reservoir area are studied. The conclusions are as follows: (1) for small rivers without data, after analyzing the sequence data of adjacent hydrological stations, the average annual runoff of Xi River calculated by hydrological analogy method and the corresponding method of precipitation runoff frequency is consistent. In accordance with the regional distribution law and the characteristics of the underlying surface. (2) by simulating the process of water and sediment movement after the dam construction, it is shown that a large amount of sediment is silted in the reservoir area by the dam construction, and its siltation form is "conical siltation"; After the dam, the flow velocity of the river decreases because of the decrease of the flow rate. (3) by simulating the short-term and long-term water and sediment processes after the dam removal, it is shown that, in the short term after the dam removal, the flow velocity of the dam site is very large because of the instantaneous and massive drainage of the reservoir, and the high water head under the dam makes the flow rate of the dam very large. As a result, the sediment in the reservoir area is cut down, the main channel scour is very serious, the crack point moves to the upstream, more sediment is eroded in the upper reaches, and the two sides of the main river channel are silted up because of the rapid drop of the water level, which results in the low velocity of the high elevation on both sides of the main river. The sediment in the lower reaches will not be silted up because the discharge velocity is too large. In the long run, there is little change in scouring and silting during the period of low water and water, but after the flood period, a large amount of sediment is transported downstream at the same time and siltation falls on both sides of the river, and the shape of the channel changes sharply upstream and develops in a narrow and deep direction. (4) compared with one-off dam removal, the downstream change is not obvious. (4) compared with one-off dam dismantling, the head difference of dam bottom is reduced, the positive and negative waves are smaller, the velocity of velocity is relatively low, the erosion is not serious enough, the distance of traceability erosion is short, but in the long run, Sediment scouring and silting distribution is similar to one-time demolition.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV147.5
[Abstract]:Reservoir dams have many functions, such as flood control and power generation, irrigation and water supply, shipping and tourism. There are about 98000 dams in China, most of which are small ones. Restricted by technology and economy at that time, many dams are deficient in planning, design, construction and management. With the approaching of service life, the negative effects of safety, economy and environment are becoming more and more prominent. For some small dams with poor safety, serious loss of function and bad ecological environment, it is a necessary management measure to carry out downgrade or scrap demolition. Compared with dam construction and operation, its scrapping and dismantling will once again upset the ecological balance of the river, cause dramatic changes in river hydrodynamic force and sediment, and indirectly affect the biological habitat of the river. At present, the rapid change of sediment situation in the reservoir area and the river channel under the dam after dam removal and its long-term ecological river profile have become a great challenge for the dam demolition project. It is of great significance to study the variation process of hydrodynamic sediment situation and its geomorphological response after dam removal. It will provide theoretical reference and technical support for dam scrapping and demolition. Based on the case of Xihe dam demolition in Guizhou Province, the process of rainfall runoff and sediment content in Xihe River basin without data are calculated through the measured topographic data and basic sediment data. A two-dimensional model of water and sediment in Xihe River is established by using Delft3D. The long-term siltation of the reservoir area before the dam removal, the short-term and long-term hydrodynamic and sediment changes of the river after the dam removal and the evolution of the river profile are simulated, respectively. At the same time, the effects of different ways of removing the dam on the sediment movement and geomorphologic change in the reservoir area are studied. The conclusions are as follows: (1) for small rivers without data, after analyzing the sequence data of adjacent hydrological stations, the average annual runoff of Xi River calculated by hydrological analogy method and the corresponding method of precipitation runoff frequency is consistent. In accordance with the regional distribution law and the characteristics of the underlying surface. (2) by simulating the process of water and sediment movement after the dam construction, it is shown that a large amount of sediment is silted in the reservoir area by the dam construction, and its siltation form is "conical siltation"; After the dam, the flow velocity of the river decreases because of the decrease of the flow rate. (3) by simulating the short-term and long-term water and sediment processes after the dam removal, it is shown that, in the short term after the dam removal, the flow velocity of the dam site is very large because of the instantaneous and massive drainage of the reservoir, and the high water head under the dam makes the flow rate of the dam very large. As a result, the sediment in the reservoir area is cut down, the main channel scour is very serious, the crack point moves to the upstream, more sediment is eroded in the upper reaches, and the two sides of the main river channel are silted up because of the rapid drop of the water level, which results in the low velocity of the high elevation on both sides of the main river. The sediment in the lower reaches will not be silted up because the discharge velocity is too large. In the long run, there is little change in scouring and silting during the period of low water and water, but after the flood period, a large amount of sediment is transported downstream at the same time and siltation falls on both sides of the river, and the shape of the channel changes sharply upstream and develops in a narrow and deep direction. (4) compared with one-off dam removal, the downstream change is not obvious. (4) compared with one-off dam dismantling, the head difference of dam bottom is reduced, the positive and negative waves are smaller, the velocity of velocity is relatively low, the erosion is not serious enough, the distance of traceability erosion is short, but in the long run, Sediment scouring and silting distribution is similar to one-time demolition.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV147.5
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相关期刊论文 前10条
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