季节性河道渗漏影响洪水演进机理及效应研究

Flood is one of the major natural disasters in the present-day world. Simulated stream flood routing calculation has realistic significance to flood control and prevention. Seepage in seasonal streams is obvious during flood season,which affects the flood flow and flood process.This research project is aimed to solve key problems for flood routing under the effect of seepage, reveal the infiltration mechanisms of seasonal streams through experiments with sand samples taken from typical stream sections and at selected testing grounds, including overall determination of the hydrological properties of sand samples (grain grading, porocity, initial water content, density, permeability, etc), soil water characteristic curve and hydraulic conductivity, indoor infiltration simulation tests (vertical and lateral), field infiltration process tests in aerated stream zones during flood season, and systematic analysis of the hydrological properties of rocks in aerated zones and correlation between hydrological data and infiltration rate of streams. It is also intended to establish infiltration formulas and use them to correct the flood routing equations, develop flood routing models with consideration of seepage and solve them ,study on the effect of seepage on seasonal flood routing, in order to provide scientific methods and basis for flood forecast, prevention and control, and comprehensive utilization of water resources in arid and semi-arid areas.

洪水灾害是当今世界面临的主要自然灾害之一，河道洪水演进模拟计算对洪水调度、防洪减灾有重要的现实意义。干旱或半干旱地区的季节性河流渗漏损失明显，直接影响行洪流量和行洪过程。本课题针对季节性河道渗漏影响洪水演进机理及效应的科学问题，选择代表性河段的砂样和试验现场，全面测定砂样的水理性质（颗粒级配、孔隙度、初始含水率、容重、渗透系数等）、水分特征曲线和水力传导度，进行室内垂向和侧向入渗模拟试验，汛期开展河道包气带入渗过程现场测试，系统分析包气带岩性的水理性质、河流水文地质数据与入渗率的相关性，揭示季节性河道入渗机理，确定入渗率数学表达式，建立并求解渗漏影响的洪水演进水动力学模型，研究渗漏对季节性河道洪水演进影响效应，从而为干旱或半旱地区河流的洪水预报、防洪减灾和水资源综合利用提供科学方法和依据。

洪水灾害是当今世界面临的主要自然灾害之一，河道洪水演进模拟计算对洪水预报、防洪减灾有重要的现实意义，而干旱或半干旱地区的季节性河流渗漏损失明显，直接影响行洪流量和行洪过程。.课题针对季节性河道渗漏影响洪水演进的关键问题，选择了代表性河段的砂样和试验现场，测定了砂样的水理性质、水分特征曲线；进行了室内垂向和侧向入渗模拟试验及数值模拟；开展了河床包气带的野外试验；建立了考虑渗漏影响的一维洪水演进数学模型，概化河道并求解了河道渗漏对洪水演进的影响效应。.研究结果：测定拟合了河道上、中、下游3种砂样的水分特征曲线，水吸力在0～10 cm水柱时，砂样含水率变化明显，随水吸力逐渐增大，含水率逐渐减小，水吸力在60cm左右水柱时，砂样含水率变化减缓，逐渐趋于平稳。细砂（下游砂样）的最大土壤水吸力最大，中砂（中游砂样）次之，粗砂（上游砂样）的最小。室内非饱和入渗试验及数值模拟、河床包气带野外入渗试验得出，河床包气带的水理性质影响着河床的入渗能力，包气带砂样越粗糙、松散，干容重越小，入渗率越大，非稳定入渗阶段持续时间越短；包气带砂层颗粒越细，干容重越大，入渗率越小，非稳定入渗阶段持续时间相对较长。总体上，入渗随时间的变化过程可分为非稳定入渗阶段和稳定入渗阶段。入渗开始阶段，入渗率迅速增加，随着入渗的进行，入渗率逐渐下降，最后趋于稳定；河道非稳定入渗过程约为1.0～1.5h，非稳定入渗量占总渗漏量的比例随时间的延长逐渐减少。数值计算并分析渗漏对河道洪水演进影响效应得出，河道渗漏对洪水演进过程产生影响，表现为流量减小，水位降低，同一断面峰值出现的时间延迟，主要影响因素是河道的入渗率，入渗率增大，影响变大。.课题获得了研究河道代表性断面的入渗规律及其对洪水演进的影响效应，研究成果可为干旱或半旱地区河流的洪水预报、防洪减灾和水资源综合利用提供科学方法和依据。