卵石滩群水沙模拟技术研究

There are many types of pebble beaches in mountain river. The formation mechanism of which are complex. The beaches are restricted by each other and waterway regulation is difficult. The regulation to gravel beach group shall be planned and designed integratedly and implemented all in one time. However currently waterway regulation technology aim single beach and far not meet formed a complete set of waterway regulation technology in beach group, which based on the physical model and focused on prototype observation or the generalized flume experiment. This study will build a two-dimensional water and sediment mathematical model based gravel transport for long period of time and long distance of river, which considered the deficiencies on the current mathematical models and focused on pebble beach group of Yibin-Chongqing river. The algorithm of the flow simulation can balance between efficiency and precision,which explore format couple explicit form and implicit form. In Bedload simulations, not only takes into account of the sediment continuity but also simulate complex pebble bedload movement by sediment mass algorithm, to the pebbles simulation quality motion goes closer to the actual. The model will validat by a series of tests and then the model is further applied in an application for investigating the change in the landform of Yibin-Chongqing river caused by the bedload transport, so that the results of this study will provide a better understanding for the complex bedload transport in waterway and provide technical support in waterway regulation of gravel beach group.

山区河流中卵石滩群的碍航特性最为复杂，整治难度非常大。目前航道整治技术多针对单滩进行，尚未形成成套的滩群整治技术，研究亦以物理模型为主，集中在卵石滩群的原型观测、概化水槽试验上。作为滩群整治研究的拓展，本研究以叙渝段卵石滩群为研究对象，采用数模模拟为手段，针对现有数学模型的不足，在水流模拟中探索不同显隐格式的嵌套，使算法能兼顾效率与精度；在推移质模拟中，突破了传统推移质模拟中仅考虑了推移质泥沙连续性，利用原创性的流团算法模拟复杂的卵石推移质运动，使卵石推移质运动过程的数值模拟更接近实际，建立以模拟卵石输移为主的二维长时段长河段水沙数学模型。通过实验数据和实测数据检验模型的计算能力，应用模型模拟叙渝段卵石滩群的河床演变过程，为以后卵石滩群整治技术的提供技术支撑。

卵石滩群的水沙计算需要解决长时段长河段非恒定流计算与推移质输沙带模拟两个难点。针对大型河流的非恒定流交汇、叠加及在长河段上的传播特性的问题，本研究采用基于隐式与显式结合的算法，提高了模型计算的效率与精度，建立了能模拟长河段非恒定流传播过程的数学模型。将该模型应用于宜宾至重庆河段的非恒定流模拟中，结果表明：该数学模型模拟水位与实测水位值基本一致，可以用于模拟该河段非恒定流传播过程。对于推移质模拟，传统的二维模型，仅考虑了推移质泥沙连续性，但由于推移质运动的连续性和水流的连续性间存在较大的时间空间不同步，加之卵石推移质运动具有很强的随机性，会造成推移质与床沙交换的位置与交换量都会与实际有很大的偏差，故数学模型很难真实反映天然山区河流推移质运动过程。为了使卵石推移质运动过程的数值模拟不断接近实际，本项目开发了推移质流团算法，兼顾了推输移速度（泥沙补给快慢），推移质沙带（推移位置），输移量（推沙率）等问题。采用数学模型模拟都江堰水利工程的卵石推移质在小水，中水，大水条件下的输移过程，通过模拟结果初步阐述都江堰“深淘滩，低作堰”这一古代工程管理总则的科学原理。