河道水位變化對岸壁穩定性影響之試驗研究

Abstract

本研究旨藉由水槽試驗探討河道水位變化對岸壁穩定之影響，並與岸壁崩塌模式比對分析，相互驗證結果之合理性。首先針對重要影響參數進行因次分析，並採用3個具代表性的無因次參數進行試驗案例的設計。正式試驗前，先選用2組案例進行重複性試驗，完成試驗流程與方法可行性的驗證。試驗材料採用矽砂與高嶺土混合，量測項目包括岸壁地下水位、河道水位、岸壁破壞位置及破壞面角度，並進行土壤基本參數試驗，含篩分析、直接剪力及定水頭滲透性試驗等。依據試驗結果，探討河道水位下降速度、岸壁坡度及初始河道水位對岸壁穩定性之影響。最後，本研究採用Chiang (2011)發展之岸壁崩塌模式進行模擬比對分析，求解孔隙水壓及岸壁穩定安全係數，藉以研判其穩定性，分析結果顯示模擬結果與量測值之整體趨勢相符。

This study aims at employing a flume experiment to analyze the influence of river-stage effect on riverbank stability. Mass failure model developed by Chiang et al. (2011) is applied to verify the experimental results. In the beginning, three dimensionless parameters for this flume experiment are derived by dimensional analysis. To ensure the repeatability, a pretest is undergone to examine designed experimental procedure. The mixture of silica sand and kaolinite is selected as experimental bank material, and is measured by sieve analysis and direct shear and permeability test. Essential terms like initial river stage, drawdown speed of river stage, and angle of river bank have been acquired in the designed experiment for analyzing their effects on riverbank stability. Due to the need of cross examination, the above-mentioned model is used to calculate pore water pressure and safety factor of riverbank. Finally, it is confirmed that flume experiment outcomes show good agreement with the result from numerical simulation.