|Alternative Title||Variation of Nearshore Wave in Three Gorges Reservoir and Its Impact on Bank Erosion|
|Place of Conferral||北京|
|Keyword||三峡水库 波浪侵蚀 近岸波浪 有效波高 护岸措施|
三峡水电站的修建，导致三峡库区水位大幅上升，水域面积更加宽阔，风力在水面的吹程急剧增加，形成较大强度的风成浪，再加上大型船舶的通航，成库后波浪对库岸沿线岸坡的侵蚀破坏将会更加剧烈。波浪侵蚀是三峡水库岸坡土壤侵蚀的重要方式，明晰水库波浪的变化特征及波浪侵蚀对岸坡水力侵蚀的贡献率，为下一步探究波浪侵蚀过程及波浪侵蚀力的数学表达奠定基础。本文主要采用野外定位观测的方法，对三峡水库不同水位运行期间不同干支流的近岸波浪参数进行统计分析，并探究波浪侵蚀强度及不同护岸措施的防护效益。论文主要结论如下：（1）三峡水库近岸波浪在空间上变化特征明显，由于长江干流与支流日均交通航运量间存在的显著差异，导致干流的波高显著大于支流，且水库同一水位运行条件下，秭归干流近岸有效波高的均值都是最大的，其次为巴东干流，说明靠近三峡大坝，航运繁忙，船行波强度最大。在时间上，波浪观测的大部分岸段均是水位越高，波浪越大。低水位时库段的最小航道实际维护尺度较高水位时有所降低，部分航道的实际维护尺度低于船舶吃水深度，特别是枯水位时，部分水域航道弯、窄、浅、险，相对较差的通航条件严重影响航运量，故低水位时水面波浪强度较高水位偏低。（2）3-Parameter Weibull分布可以描述三峡水库近岸波浪的波高分布情况，对于确定三峡水库波浪对岸坡的荷载具有重要意义。相对于支流岸段所测数据，干流波高累积频率分布曲线的变化趋势较平缓，说明干流波高分布区间广，大波高发生频繁，与支流存在着显著差异。库面的宽度对波浪的传播产生显著的影响，波浪受到不同的底摩擦阻力，能量随之发生改变，这可能是引起库面宽阔岸段的有效平均波高小于狭窄岸段的原因。三峡水库水面波浪主要受库面风力和行船的影响，风引起的主要为小于3cm的波浪，大于3cm的波浪主要由行船引发。行船对三峡水库近岸波浪的波高变化有着极大的影响，这样会造成波浪能量的变化，从而对库岸沿线自然边坡和路基边坡产生不同程度的侵蚀。（3）三峡水库库岸波浪侵蚀强度远远大于降雨径流侵蚀强度，波浪侵蚀占到总侵蚀的70%-80%，说明三峡水库波浪对水库岸坡土壤侵蚀具有重要影响。尽管狗牙根可以显著降低土壤侵蚀强度，减蚀效应达到28% ，但远远低于植生砖生态护坡措施66%的减蚀效应。此外，植生砖生态护岸试验区内的土壤抗剪切强度也远远大于狗牙根护岸，说明生态护坡的防护效益好，适用于三峡水库岸坡防护工程。;
The construction of the Three Gorges Hydropower Station led to a substantial rise of water level in the Three Gorges Reservoir, so that the water area becomes more spacious and the wind fetch increases sharply. Coupled with the navigation of large vessels, the damage on the bank slope made by nearshore waves will be more intense. Wave erosion is an important way of soil erosion in the Three Gorges Reservoir bank. In order to lay a foundation for exploring wave erosion processes and mathematical expression of wave erosion force, it is important to make clear of the variation of nearshore waves and the contribution rate of wave erosion to the water erosion in Three Gorges Reservoir. By using in-situ observation method, this paper statistically analyzes the nearshore wave parameters of different mainstreams and tributaries during different water level period and explores wave erosion intensity and the benefits of distinct bank protection measures in Three Gorges Reservoir . The main conclusions of this paper are as follows:The spatial variation of nearshore waves in the Three Gorges reservoir is quite obvious. Due to the significant difference of the average daily shipping traffic amount between the Yangtze River mainstreams and tributaries, the average wave height along the bank of mainstream is higher than that along the bank of tributary, and under the same water level operating conditions, the significant wave height (SWH) in Zigui reach of Three Gorges Reservoir is the largest, followed by Badong reach, resulting from that near the Three Gorges Dam, the shipping is busy, and the intensity of wave led by ship is the biggest. In time, the higher the water level is, the bigger the wave is in most part of the observation sites. The actual minimum channel maintenance dimension during the low water level is reduced compared with high water level and the actual maintenance dimension of some channel is lower than ship draft depth. Part of the water channel is curved, narrow, shallow and dangerous. Relatively poor navigation conditions seriously affect the amount of shipping so that the wave intensity of low water level is weaker than that of high water level. 3-Parameter Weibull distribution can well describe the nearshore wave height distribution of the Three Gorges Reservoir, which is of great significance for the determination of wave load on the slope of the Three Gorges Reservoir. With respect to the measured data in tributaries, the cumulative frequency distribution curve of mainstream wave height is relatively flat, indicating that the wave height distribution range of mainstream is wide and high waves occur frequently. Waterway width exert significant impact on the nearshore wave height. The wave is subjected to different frictional resistance, and the energy is changed. This may be the cause that the average SWH over narrow river surface is smaller than that over broad river surface. Three Gorges reservoir water surface wave is mainly affected by the wind and shipping. The wave smaller than 3cm is mainly cause by wind and the shipping primarily triggers big wave that are higher than 3cm. Sailing in the Three Gorges Reservoir has a significant impact on the variation of nearshore wave height, this will result in changes in wave energy, and thus the natural reservoir bank slope and embankment slope along different degrees of erosion.The intensity of wave erosion in Three Gorges Reservoir is far greater than that of runoff erosion, wave erosion accounted for 70%-80% of the total erosion, indicating that the waves have a significant impact on bank erosion of the Three Gorges Reservoir. Although Bermudagrass can significantly reduce the intensity of soil erosion, with the erosion reduction effect reaching 28%, but much lower than the reduction erosion effect of raw brick plant ecological slope protection measures, which is 66%. In addition, the soil shear strength in the area of raw brick plant ecological slope protection measures is far greater than that of Bermudagrass revetment, which illuminates ecological bank protection measure has better protection efficiency and is suitable for the bank slope protection engineering of Three Gorges Reservoir.
|李峪. 三峡水库波浪变化特征及其对库岸土壤侵蚀的影响[D]. 北京. 中国科学院大学,2016.|
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