三峡库尾卵石滩群再造过程及航槽适应性协调机制研究

Under the new hydrological conditions, the Three Gorges reservoir tail will encounter the obstruction problems caused by reformation process of gravel beach groups in a long run. The development of Changjiang River economic belt calls for the further improvement of waterway dimension in the Three Gorges reservoir tail, combined with the restriction of field observation technology and the insufficient existing bed-load transport theory as well as the great difficulty in waterway regulation of the Three Gorges reservoir tail, therefore it is urgent to conduct an intensive study on the reformation process of gravel beach groups in the Three Gorges reservoir tail and the waterway adjustment methods. This project, in the aspect of mechanism and through the field experiments in Chongqing reach as well as the 12m high-precision varied-slope flume laboratory experiment, studies the dynamic relationship between the multi-scale turbulent structures and the bed-load transport; through the field observation and experiment of bed-load transport in Jiu Long Po reach as well as generalization of glass flume experiment in an alternate wide shallow and narrow deep form, the project also studies the dynamic characteristics of key imbalanced bed-load transport processes in a wide shallow and narrow deep form. On a theoretical aspect, on the basis of the multi-scale turbulent structure movement characteristics and the kinetics theory of sediment movement in the open channels, the project builds a bed-load transport mechanical model based on multi-scale turbulent structures. On the application aspect, through the predicted model and the entity model of the reformation process of gravel beach groups in the Three Gorges reservoir tail, the project predicts the evolution trend of the Three Gorges reservoir tail and seeks the regulation methods for the typical gravel shallow waterway.

三峡库尾河段在新水沙条件下，将长期面临卵石滩群再造过程导致的碍航问题。长江经济带的发展要求三峡库尾河段的航道尺度进一步提高，但受卵石运动野外观测技术及现有推移质输移理论还不充分的制约，三峡库尾河段整治难度大，因此迫切需要深入研究三峡库尾卵石滩群再造过程及航槽适应性调整方法。本项目在机理层面，通过三峡库尾九龙坡河段现场观测和12m高精度变坡水槽试验，研究多尺度湍流结构与卵石群体输移的动力性关系；通过三峡库尾九龙坡河段推移质输移现场观测和概化水槽试验，研究宽浅-窄深交替形态不平衡推移质输移的关键性过程的动力学特性。在理论层面，以多尺度湍流结构运动特性为基础，建立基于多尺度湍流结构的推移质造床力学模型。在应用层面，建立三峡库尾卵石滩群再造预测模型，预测三峡库尾河段演变趋势；通过实体模型，寻求三峡库尾卵石滩群航槽适应性协调机制和整治方法。

本项目主要研究三峡库尾河段新水沙条件下的卵石滩群再造过程及航槽适应性调整方法，已按计划完成研究任务。三峡库尾河段在卵石滩群再造过程的影响下，受卵石运动野外观测技术及现有推移质输移理论还不充分的制约，导致河段整治难度大，航道尺度提升困难。尽管现有的关于三峡水库泥沙、推移质输移、河床演变数学模型以及航道整治方面开展了众多的研究，取得了很多有意义的成果，但仍然很难对卵石滩群的再造过程及对航槽如何影响的问题认识清楚。本项目针对上述问题开展研究，取得的主要进展有：（1）通过开展三峡库尾重庆九龙坡河段现场观测，及精细水槽室内实验，利用ADCP及三维 PIV 测量技术，精细测量明渠多尺度湍流结构和卵石沙波的形态变化，分析了多尺度湍流结构与卵石群体输移机理；（2）利用基于水下声学测量技术和测坑对重庆九龙坡河段的卵石输移进行长时间的观测，分析该河段水库消落期和洪水期的卵石输移的时间和空间分布；开展宽浅-窄深全玻璃概化水槽室内试验，利用三维 PIV 和 PTV技术精细测量宽浅-窄深河段不同流量下明渠多尺度湍流结构和卵石输移路径变化，分析了推移质输移的关键性过程的动力学特性；（3）结合多尺度湍流结构下卵石起动及运动周期试验研究，揭示了卵石推移质起动的临界流速，获得了湍流结构与卵石运动周期性关系的量化指标，明确了卵石运动的力学物理过程，确定了三峡库尾卵石运动的力学模式，建立了基于多尺度湍流结构推移质造床力学模型，并通过验证；（4）基于推移质造床力学模型，建立了以三峡库尾卵石滩群为独立单元的推移质造床模拟理论和方法，预测了三峡库尾卵石滩群再造过程，结合试题模型试验，提出了卵石滩群协同控导整治技术并在重点滩段开展示范应用。.本项目深入探析了三峡水库库尾卵石滩群再造演变的动力学过程，开展了大量研究寻求三峡库尾航槽适应性协调机制和整治方法。项目研究成果可以填补泥沙运动力学、河流动力学和河床演变学的理论空白，为三峡库尾卵石碍航机理的揭示及航道调控方法研究提供重要支撑，对于长江黄金水道航运开发具有重要的实践意义。