Karst地区伏流水沙输移机理研究

In the southwest of the country, sinking streams in karst regions are very common. In these areas, damming will encounter complicated pressurized flow sediment deposition problem, which will affect the safety of flood control, reservoir working life and the like. Currently, there is a lack of systematic research on the mechanism of cognition. In this study, the sediment transport mechanism specifically for karst regions would be studied through theoretical analysis, data analysis, and generalized flume experiment. Data analysis would be conducted to explore the characteristics of pressurized flow and sediment transport. In flume experiments, different changes of flow, sediment and backwater conditions would be purposely designed to study the flow structure characteristics, sediment transport and bed evolution of the sinking and entrance sections. Furthermore, based on the theoretical analysis, propose the theory and method describing sediment transport by pressurized flow, and reveal the interaction mechanism between pressurized flows, sediment transport and river evolution in sinking streams. The results of this study can enrich and improve the river sediment dynamics, riverbed evolution and other disciplines, and has important application value in engineering.

我国西南部Karst地区溶洞伏流广泛存在，该地区筑坝蓄水将遇到库区溶洞伏流泥沙淤积问题，处理不当将影响防洪安全、综合效益、水库寿命等，目前国内外缺乏系统的研究和机理上的认识。本项目将从上游不同水沙和下游不同壅水条件下溶洞伏流的水流运动、泥沙输移、河床演变规律着手，采用资料分析、概化水槽试验、理论分析等研究手段，深入研究Karst地区伏流水沙输移机理。通过实测资料分析，探讨Karst地区天然伏流河段水沙输移特性；采用概化水槽试验，研究不同来流量和壅水程度条件下伏流及口门上下游明流段水流结构特征的变化规律，不同水沙和壅水组合条件下伏流及口门上下游明流段泥沙输移、河床演变规律；基于理论分析，建立描述伏流水沙输移的理论和方法，揭示溶洞伏流水动力场、动水压力场、泥沙输移、河床演变规律及相互作用机制。本项目研究成果可丰富和完善河流泥沙动力学、河床演变学等学科，同时具有重要的工程应用价值。

针对西南Karst岩溶地区伏流河道筑坝后泥沙淤积严重甚至堵塞影响水库安全运行和水生态环境的问题，从上游不同水沙和下游不同壅水条件下溶洞伏流的水流特性、泥沙输移及河床演变规律着手，采用实测资料分析、概化水槽试验、理论分析、水沙数学模型等研究手段协同开展工作，掌握了天然溶洞伏流河段形态特征和水沙运动特点，阐明了天然和壅水条件下伏流段及上游明流段水位、压力、紊动、泥沙冲淤、河床演变及泥沙级配变化规律，揭示了明满流交替条件下伏流河段内外混合流运动、泥沙输移与河床演变机理，从纵向水力比降、挟沙能力、伏流洞断面面积变化及相互作用关系角度阐明了伏流洞泥沙淤积平衡机制，初步构建了非规则断面过流通道明渠与承压水流的统一描述方法、河床动态冲淤的模拟技术及混合流水沙输移模拟理论，并结合国家172项重大水利工程—贵州夹岩水利枢纽工程开展了一、三维混合流水沙数学模型计算，为工程设计论证提供坚实的科技支撑。研究成果丰富了河流泥沙运动力学、河床演变学，可在Karst岩溶地区伏流河道治理、水电开发推广应用。