Study on Mechanism of Local Scour in downstream of Bed Protection Works

本文研究护床工程下游的冲刷问题，以建立合理的护床工程设计。本研究的主要结论如下：1.对海尔肯河宽堰段和涵洞段的泥沙冲刷进行了实地调查，2.对三种护床方式下的床面糙率纵向突变进行了试验研究动床荷载作用下的动床工程。分析了床面剖面和最大冲刷孔深度的变化规律，并测定了冲刷各阶段的水流特性。3.在此基础上，提出了采用边界拟合坐标系对护床工程下游河床冲刷进行二维数值模拟的方法，并应用于试验研究。数值计算结果与实验结果的对比验证了该模型对冲刷过程的预测能力

THIS STUDY DEALS WITH LOCAL SCOUR IN DOWNSTREAM OF BED PROTECTION WORKS IN ORDER TO ESTABLISH THE REASONABLE DESIGN OF THE BED PROTECTION WORKS. THE CONCLISIONS OF THIS STUDY CAN BE DRAWN AS FOLLOWS.1.A DETAILD FIELD SURVEY WAS CARRIED OUT REGARDING LOCAL SCOUR AT THE SECTION OF NINOARATE WEIR HAVING A BROAD CRESTE AND CULVERTS IN HYAKKEN RIVER, PREPARATIONS FOR MEASURING STREAM CONDITIONS AND SCOUR DEPTH AT A FLOOD WERE MADE.2.THE EXPERIMENTS WERE CARRIED OUT IN CASE OF SUDDEN CHANGE IN BED ROUGHNESS LONGITUDINALLY FROM A ROUGH BED CONSISTING OF THREE TYPES OF BED PROTECTION WORKS TO A MOVABLE BED UNDER DYNAMIC CONDITION OF BED LOAD. VARIATIONS OF BED PROFILE AND THE MAXIMUM DEPTH OF SCOUR HOLE WERE DISCUSSED AND FLOW CHARACTERISTICS WERE MEASURED AT SEVERAL STAGES OF SCOUR. AS THE RESULT, A METHOD TO REDUCE SCOUR DEPTH BY USING RICH-IN-NATURE TYPE RUBBLE WORKS WAS PROPOSED.3.BASED ON THESE RESULTS, 2-D NUMERICAL SIMULATIONS FOR LOCAL SCOUR IN DOWNSTREAM OF BED PROTECTION WORKS USING BOUNDARY FITTED COORDINATE SYSTEM WERE PROPOSED AND APPLIED TO THE EXPERIMENTS. COMPARING THE NUMERICAL AND EXPERIMENTAL RESULTS VERIFIED THE ABILITY OF THIS MODEL TO PREDICT THE SCOUR PROCESS