长江口最大浑浊带水沙特性研究
发布时间：2019-05-23 10:39
【摘要】：河口最大浑浊带作为河口区中的一个特殊区段,是河口径流、潮汐等相互作用的产物,其实质是泥沙的沉积动力过程。最大浑浊带具有高含沙量、高浊度的特性,它直接影响着沉积过程中细颗粒泥沙的聚集和输移,进而对河口滩槽的发育与演变起到显著的影响。长江口横沙浅滩、九段沙以及北槽深水航道都位于最大浑浊带,研究最大浑浊带水沙运动,探索河口浅滩和拦门沙的形成、发育及演变规律,对该地区的工程整治及建设有着十分重大的意义。 本文基于1982年洪枯季、2011年枯季与2013年洪季长江口浑浊带水域多测点实测水文泥沙资料,对浑浊带水沙时空特性进行了系统分析。根据多点连续实测数据,阐述长江口最大浑浊带水域水动力的时空特征；并在此基础上对最大浑浊带悬沙浓度及粒度特征进行分析,包括平面分布、垂向分布以及周期性特征；对比1982年与2011年枯季、2013年洪季长江口最大浑浊带的水沙特性,分析30年来最大浑浊带的水沙特征变化；通过计算各测点单宽悬沙通量以及分解通量机制,了解浑浊带泥沙输运规律和动力控制因子。 主要结论如下： (1)从最大浑浊带外缘向内到核心区域,潮流从旋转流过渡为往复流。洪枯季流速大小比较接近,但是洪季流速方向角度普遍要大于枯季,这是因为径流通过长江口在科氏力的作用下向南偏,使得涨潮时,流速偏向西北,落潮时流速偏向东南。大潮涨落潮流速大于小潮涨落潮流速,最大可达到相差2倍以上。在北港和北槽纵向上,从内向外,流速大体上逐渐减小,在南汇浅滩外,从内向外,流速逐渐增加。横向上比较,位于浑浊带核心区的点流速从北向南逐渐减小,而在浑浊带外缘,从北向南,流速逐渐增大,但是最大流速仍然出现在最大浑浊带核心区域。 (2)浑浊带核心区流速梯度最大,在最大浑浊带核心区,三个汊道对比：北港北槽南槽,而在浑浊带外缘,北港北槽南槽；在南汇外,水动力情况比较类似,三者的流速梯度基本都在0.04s-1左右,所以整体上北港内流速梯度最大,北港外流速梯度最小。在潮周期内最大垂向流速梯度一般出现在涨急或落急时刻前后,且一般落急流速梯度更大。 (3)从最大浑浊带核心区到外缘,悬沙浓度逐渐降低,且最大浑浊带核心区浓度远高于其他区域,在大潮时,核心区悬沙浓度与外缘的比值在2.8～13倍之间；大潮水动力条件强于小潮,使得大潮悬沙浓度较小潮高,最高可为小潮悬沙浓度的14倍；在开阔水域,研究区域受到风浪掀沙,枯季泥沙起动强度大,悬沙浓度较洪季大。各点悬沙浓度受到水流动力强弱影响会随时间会出现周期性的变化,由于泥沙再悬浮的滞后性,最大悬沙浓度一般出现在急流时刻后1-2h,北港枯季大潮和南槽洪季大潮水体再悬浮能力强,在低潮位时,整体水体深度上悬沙浓度都很大。最大浑浊带3个主槽悬沙浓度一般北槽悬沙浓度最大,南槽次之,北港最小。 (4)浑浊带核心区悬沙中值粒径较外缘大,在大潮时,差距超过50%,而在小潮时核心区悬沙中值粒径略小于外缘。对比浑浊带核心区三个汊道的悬沙中值粒径,北槽最大,其次为南槽,北港最小。一般在大潮时,水体动力强,悬沙中值粒径较小潮时大,而且只有在大潮时悬沙中才会出现砂的成分,且在北槽中悬沙三组分中砂的含量最多。 (5)近30年来长江口年径流量基本无变化,年输沙量减少了近60%,长江口浑浊带整体流速大小变化不大,只有在浑浊带核心区流速出现相对较大的差别,2011、2013年大潮时流速较1982年同期增大20%左右,小潮流速减小了15%左右,外缘流速相差很小,增减幅度不超过10%。近30年来悬沙浓度有明显减小,2011、2013年悬沙浓度较1982年同期减少了50%左右。 (6)通过计算浑浊带水域悬沙通量,发现整体上北港悬沙通量向东输送,北槽向东南输送,南汇外靠内测点主要在南北方向上来回输送,浑浊带外缘悬沙向东南方向输运。悬沙通量受悬沙浓度和流速大小的影响,一般大潮大于小潮；最大浑浊带外边缘洪枯季悬沙通量对比特征不明显,而在核心区洪季悬沙通量要大于枯季。最大浑浊带核心区的悬沙通量较外缘要大,3个汉道北槽悬沙通量最大。通过机制分解法进行分析,发现平流输移项和潮泵效应项是长江口最大浑浊带的主要输沙机制,在最大浑浊带核心区以平流输移项为主,主要向海输沙,在浑浊带外缘以潮泵效应项向陆输沙为主,阻碍悬沙向海输移,这也是造成浑浊带核心区泥沙淤积的原因之一。 通过对长江口最大浑浊带水沙特性的分析,发现在最大浑浊带核心区水动力最强,流速梯度最大,强水动力和强底层流速梯度能造成底部泥沙剧烈起动,造成水体悬沙的高中值粒径,整个水体的强流速梯度能使水体维持高悬浮泥沙浓度状态；在最大浑浊带核心区,向海输沙的平流输移项占主导,在浑浊带外缘,则以向陆输沙的潮泵效应为主,阻碍悬沙向海输移,使得最大浑浊带区域泥沙聚集,形成了最大浑浊带；而最强的水动力和高悬沙浓度,使得最大浑浊带核心区的悬沙单宽通量最大。
[Abstract]:The largest turbidity zone in the estuary, as a special section in the river mouth area, is the product of the interaction of the river mouth runoff, the tide and the like, the essence of which is the sediment dynamic process of the sediment. The maximum turbidity zone has the characteristics of high sediment concentration and high turbidity, which directly influences the accumulation and transport of fine-grain sand in the deposition process, and further has a remarkable effect on the development and evolution of the river-mouth beach. It is of great significance to study the formation, development and evolution of the river-mouth shoal and the sand-retaining sand, and to explore the formation, development and evolution of the river-mouth shoal and the sand-retaining sand in the cross-sand shoal, the nine-section sand and the deep-water channel of the north trough, and to explore the formation, development and evolution of the river-mouth shoal and the sand-retaining sand. The time-and-space characteristics of the muddy water and sand are systematically divided based on the measured hydrological and sediment data of the multi-measuring points in the turbid zone of the Yangtze River estuary in the dry season of 1982, the dry season of 2011 and the flood season in the Changjiang Estuary in 2013. In this paper, the temporal and spatial characteristics of the water power in the maximum turbidity zone in the Yangtze River estuary are described based on the multi-point continuous measured data, and the suspended sediment concentration and the particle size characteristics of the maximum turbidity zone are analyzed on the basis of the data, including the plane distribution, the vertical distribution and the periodicity. The characteristics of the water and sediment of the largest turbid zone in the Yangtze River estuary in the Yangtze River Estuary in the first quarter of 2013 and the dry season of 2011 are compared. The change of the water and sediment characteristics of the largest turbid zone in the past 30 years is analyzed. By means of the calculation of the single-width suspended sediment flux and the decomposition flux mechanism of each measuring point, the sediment transport law and the power control of the turbidity belt are known. Primary junction The theory is as follows: (1) from the outer edge of the largest turbid zone to the core area, the tide flows from the rotation The flow velocity of the flood season is close to that of the flood season, but the flow direction of the flood season is generally greater than the dry season, because the runoff is shifted to the south by the influence of the Coriolis force by the Yangtze River estuary, so that the flow velocity is biased to the northwest and the tide is in the ebb tide. The speed of the spring tide is greater than the tidal current speed of the small tide, and the maximum can reach the phase. 2 times the difference. In the longitudinal direction of the north and the north, the flow rate is gradually reduced from inside to outside, outside the Bank of Nanhui, from inside to outside, flow The velocity is gradually increased. In the transverse direction, the point flow rate in the core area of the turbid zone gradually decreases from the north to the south, and at the outer edge of the turbid zone, the flow rate gradually increases from the north to the south, but the maximum flow rate is still at the maximum turbidity. With the core area, (2) the maximum velocity gradient of the core area of the turbid zone is the largest in the core area of the largest turbid zone, and in the core area of the largest turbid zone, the three main channels are compared: the south trough of the north trough of the north port, and the south trough of the north trough of the north port on the outer edge of the turbid zone; and the water power situation is similar in the south of the south sink, and the flow rate gradient of the three is basically zero. It is about 04s-1, so the velocity gradient in the whole north port is the largest, and the north port The gradient of the external flow velocity is the least. The maximum vertical velocity gradient in the tidal cycle generally occurs before and after the rising or falling time, and generally falls (3) The concentration of suspended sand is gradually reduced from the core area of the largest turbid zone to the outer edge, and the concentration of the core area of the largest turbid zone is much higher than that of the other regions. In the spring tide, the ratio of the concentration of suspended sand to the outer edge of the core area is between 2.8 and 13 times, and the spring tide The water dynamic condition is stronger than that of the small tide, so that the suspended sediment concentration of the spring tide is high, and the maximum can be 14 times of the suspended sediment concentration of the small tide; in the open water area, the research area is affected by the wind wave and the sand, and the starting strength of the dry season sediment is large The concentration of suspended sand is larger than that of the flood season. The concentration of suspended sand at each point is affected by the dynamic strength of the water flow, which can change with the time. Due to the lag of the re-suspension of the sediment, the maximum suspended sediment concentration is generally 1-2h after the time of the jet, and the spring tide of the northern port and the water body re-suspension in the spring of the flood season in the south trough. The ability is strong, at low tide level, the whole body of water is deep The suspended sediment concentration in the maximum turbidity zone is the largest, and the concentration of suspended sand in the north trough is the largest. The south channel is the second and the north port is the smallest. (4) The median particle size of the suspended sand in the core area of the turbid zone is larger than that of the outer edge. In the spring tide, the gap is more than 50%, while in the core area of the small tide The median particle size of the suspended sand is slightly smaller than the outer edge. The median particle size of the suspended sand in the three main channels in the core area of the turbid zone is compared with that of the north trough. The second is the south trough and the north port is the smallest. Generally, in the spring tide, the water body power is strong, the median particle size of the suspended sand is small, and only the sand is present in the suspended sand during the spring tide, and the sand is suspended in the north groove The content of sand in the three-component sand is the most. (5) The annual runoff of the Yangtze River estuary has not changed basically in the past 30 years, the annual sediment concentration is reduced by nearly 60%, and the change of the whole flow velocity of the turbid zone in the Yangtze River estuary is not large, and only in the area of the core area of the turbid zone, the flow velocity is less than 1 in the spring tide of 2011 and 2013. In the same period of the same period in the year of 982, about 20%, the small flow rate was reduced by about 15%, and the flow rate of the outer edge was different. In recent 30 years, the suspended sediment concentration has been significantly reduced, and the suspended sediment concentration in 2011 and 2013 is 19. In the same period, about 50% was reduced in the same period in the same period. (6) Through the calculation of the suspended sediment flux in the water area of the turbid zone, it is found that the floating sand flux in the north port of the whole is transported to the east, and the north groove is transported to the southeast, and the inner measuring point of the south sink is mainly transported back and forth in the north-south direction. The flux of suspended sand is affected by the concentration of suspended sand and the flow velocity, and the general spring tide is larger than that of the small tide; the contrast of the suspended sediment flux in the maximum turbid out-of-band edge is not obvious. The suspended sediment flux in the core area of the core area is greater than the dry season, and the suspended sediment flux in the core area of the largest turbid zone is lower than the outer edge The maximum suspended sediment flux in the north trough of the three Han channels is the largest. Through the analysis of the mechanism decomposition method, it is found that the advection transfer term and the tidal pump effect term are the main sediment transport mechanism of the largest turbid zone in the Yangtze River estuary. It is also caused by the fact that the outer edge of the belt is dominated by the tidal pump effect and is mainly used for transporting sand to the sea, and the suspended sand is prevented from being transported to the sea, which is also caused The cause of sediment deposition in the core area of the turbid zone is one of the causes of silting in the core area of the turbid zone. Through the analysis of the characteristics of the water and sediment in the largest turbidity zone in the Yangtze River Estuary, it is found that the maximum hydrodynamic force, the maximum velocity gradient, the strong water power and the strong bottom layer flow velocity gradient in the core area of the largest turbidity zone can cause the bottom sediment the high-school value particle size of the suspended sediment in the water body is caused by severe starting, the strong flow velocity gradient of the whole water body can enable the water body to maintain a high suspended sediment concentration state, The tidal pump effect of the sand is the main reason, and the suspended sand is prevented from being transported to the sea, so that the sediment in the maximum turbid zone is collected, the largest turbid zone is formed, and the strongest water power and the high suspended sediment concentration are made,
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV148
[Abstract]:The largest turbidity zone in the estuary, as a special section in the river mouth area, is the product of the interaction of the river mouth runoff, the tide and the like, the essence of which is the sediment dynamic process of the sediment. The maximum turbidity zone has the characteristics of high sediment concentration and high turbidity, which directly influences the accumulation and transport of fine-grain sand in the deposition process, and further has a remarkable effect on the development and evolution of the river-mouth beach. It is of great significance to study the formation, development and evolution of the river-mouth shoal and the sand-retaining sand, and to explore the formation, development and evolution of the river-mouth shoal and the sand-retaining sand in the cross-sand shoal, the nine-section sand and the deep-water channel of the north trough, and to explore the formation, development and evolution of the river-mouth shoal and the sand-retaining sand. The time-and-space characteristics of the muddy water and sand are systematically divided based on the measured hydrological and sediment data of the multi-measuring points in the turbid zone of the Yangtze River estuary in the dry season of 1982, the dry season of 2011 and the flood season in the Changjiang Estuary in 2013. In this paper, the temporal and spatial characteristics of the water power in the maximum turbidity zone in the Yangtze River estuary are described based on the multi-point continuous measured data, and the suspended sediment concentration and the particle size characteristics of the maximum turbidity zone are analyzed on the basis of the data, including the plane distribution, the vertical distribution and the periodicity. The characteristics of the water and sediment of the largest turbid zone in the Yangtze River estuary in the Yangtze River Estuary in the first quarter of 2013 and the dry season of 2011 are compared. The change of the water and sediment characteristics of the largest turbid zone in the past 30 years is analyzed. By means of the calculation of the single-width suspended sediment flux and the decomposition flux mechanism of each measuring point, the sediment transport law and the power control of the turbidity belt are known. Primary junction The theory is as follows: (1) from the outer edge of the largest turbid zone to the core area, the tide flows from the rotation The flow velocity of the flood season is close to that of the flood season, but the flow direction of the flood season is generally greater than the dry season, because the runoff is shifted to the south by the influence of the Coriolis force by the Yangtze River estuary, so that the flow velocity is biased to the northwest and the tide is in the ebb tide. The speed of the spring tide is greater than the tidal current speed of the small tide, and the maximum can reach the phase. 2 times the difference. In the longitudinal direction of the north and the north, the flow rate is gradually reduced from inside to outside, outside the Bank of Nanhui, from inside to outside, flow The velocity is gradually increased. In the transverse direction, the point flow rate in the core area of the turbid zone gradually decreases from the north to the south, and at the outer edge of the turbid zone, the flow rate gradually increases from the north to the south, but the maximum flow rate is still at the maximum turbidity. With the core area, (2) the maximum velocity gradient of the core area of the turbid zone is the largest in the core area of the largest turbid zone, and in the core area of the largest turbid zone, the three main channels are compared: the south trough of the north trough of the north port, and the south trough of the north trough of the north port on the outer edge of the turbid zone; and the water power situation is similar in the south of the south sink, and the flow rate gradient of the three is basically zero. It is about 04s-1, so the velocity gradient in the whole north port is the largest, and the north port The gradient of the external flow velocity is the least. The maximum vertical velocity gradient in the tidal cycle generally occurs before and after the rising or falling time, and generally falls (3) The concentration of suspended sand is gradually reduced from the core area of the largest turbid zone to the outer edge, and the concentration of the core area of the largest turbid zone is much higher than that of the other regions. In the spring tide, the ratio of the concentration of suspended sand to the outer edge of the core area is between 2.8 and 13 times, and the spring tide The water dynamic condition is stronger than that of the small tide, so that the suspended sediment concentration of the spring tide is high, and the maximum can be 14 times of the suspended sediment concentration of the small tide; in the open water area, the research area is affected by the wind wave and the sand, and the starting strength of the dry season sediment is large The concentration of suspended sand is larger than that of the flood season. The concentration of suspended sand at each point is affected by the dynamic strength of the water flow, which can change with the time. Due to the lag of the re-suspension of the sediment, the maximum suspended sediment concentration is generally 1-2h after the time of the jet, and the spring tide of the northern port and the water body re-suspension in the spring of the flood season in the south trough. The ability is strong, at low tide level, the whole body of water is deep The suspended sediment concentration in the maximum turbidity zone is the largest, and the concentration of suspended sand in the north trough is the largest. The south channel is the second and the north port is the smallest. (4) The median particle size of the suspended sand in the core area of the turbid zone is larger than that of the outer edge. In the spring tide, the gap is more than 50%, while in the core area of the small tide The median particle size of the suspended sand is slightly smaller than the outer edge. The median particle size of the suspended sand in the three main channels in the core area of the turbid zone is compared with that of the north trough. The second is the south trough and the north port is the smallest. Generally, in the spring tide, the water body power is strong, the median particle size of the suspended sand is small, and only the sand is present in the suspended sand during the spring tide, and the sand is suspended in the north groove The content of sand in the three-component sand is the most. (5) The annual runoff of the Yangtze River estuary has not changed basically in the past 30 years, the annual sediment concentration is reduced by nearly 60%, and the change of the whole flow velocity of the turbid zone in the Yangtze River estuary is not large, and only in the area of the core area of the turbid zone, the flow velocity is less than 1 in the spring tide of 2011 and 2013. In the same period of the same period in the year of 982, about 20%, the small flow rate was reduced by about 15%, and the flow rate of the outer edge was different. In recent 30 years, the suspended sediment concentration has been significantly reduced, and the suspended sediment concentration in 2011 and 2013 is 19. In the same period, about 50% was reduced in the same period in the same period. (6) Through the calculation of the suspended sediment flux in the water area of the turbid zone, it is found that the floating sand flux in the north port of the whole is transported to the east, and the north groove is transported to the southeast, and the inner measuring point of the south sink is mainly transported back and forth in the north-south direction. The flux of suspended sand is affected by the concentration of suspended sand and the flow velocity, and the general spring tide is larger than that of the small tide; the contrast of the suspended sediment flux in the maximum turbid out-of-band edge is not obvious. The suspended sediment flux in the core area of the core area is greater than the dry season, and the suspended sediment flux in the core area of the largest turbid zone is lower than the outer edge The maximum suspended sediment flux in the north trough of the three Han channels is the largest. Through the analysis of the mechanism decomposition method, it is found that the advection transfer term and the tidal pump effect term are the main sediment transport mechanism of the largest turbid zone in the Yangtze River estuary. It is also caused by the fact that the outer edge of the belt is dominated by the tidal pump effect and is mainly used for transporting sand to the sea, and the suspended sand is prevented from being transported to the sea, which is also caused The cause of sediment deposition in the core area of the turbid zone is one of the causes of silting in the core area of the turbid zone. Through the analysis of the characteristics of the water and sediment in the largest turbidity zone in the Yangtze River Estuary, it is found that the maximum hydrodynamic force, the maximum velocity gradient, the strong water power and the strong bottom layer flow velocity gradient in the core area of the largest turbidity zone can cause the bottom sediment the high-school value particle size of the suspended sediment in the water body is caused by severe starting, the strong flow velocity gradient of the whole water body can enable the water body to maintain a high suspended sediment concentration state, The tidal pump effect of the sand is the main reason, and the suspended sand is prevented from being transported to the sea, so that the sediment in the maximum turbid zone is collected, the largest turbid zone is formed, and the strongest water power and the high suspended sediment concentration are made,
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV148
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