石門水庫上游流域沿岸之邊坡,坡腳受到河流侵蝕,容易造成邊坡不穩定而引發再次滑動;回顧近年來台灣坡地災害頻傳,其中黏土質崩積層崩塌之災害事件更是其中大宗,其崩塌量體大往往造成大規模慘重災情,如梨山地區崩塌、紅菜坪崩塌、草嶺、九份二山崩塌形成堰塞湖等事件之慘痛先例,顯見臨河岸的大規模粘土質崩積層崩塌滑動所衍生之後續災害與威脅性實更是不容忽視。 本研究主要係以果凍添加砂進行小型室內物理模型之侵蝕試驗。邊坡組成材料中常見的有砂土質與黏土質。砂土質邊坡顆粒間沒有凝聚力,邊坡堆積通常小於砂土的安息角;黏土質的顆粒粒徑較小,顆粒間存在凝聚力而使得黏土質自立性佳。為了模擬出似黏土質邊坡材料之凝聚力,本研究以模擬加入海菜粉後的邊坡材料—果凍添加砂—受到侵蝕行為之運動過程與破壞形式,並與無凝聚力的乾砂做比較。果凍添加砂邊坡試體發生破壞時可於冠部見到張力裂縫的發展,並依開裂的特徵探討其成因,並利用PIV討論形成張力裂縫後的邊坡分離塊體運動模式。最後透過顆粒力學方法PFC3D軟體進行模擬驗證。由試驗結果歸納出侵蝕力主控與坡面傾度主控之張力裂縫,張力裂縫產生之分離塊體主要往坡面傾度最大的方向運動。
Along the upper reaches basin of Shihmen Reservoir, there are cases of clay colluviums are eroded at the bank by rivers. Cases like these lead to slope instability, which often cause further sliding. Recall geological disasters in Taiwan Recently, most of the disasters happen to be clay colluviums slope failures, which will occur serious disaster such as landslide of Lishan region, Hungtsaiping landslide etc. Above cases tell the clay colluviums cut at river banks are too menacing to ignore. This Study discusses physical model test of erosion using low-cohesive material, jelly-mixed sand. Using jelly-mixed sand as slope material provide advantages of easy add cohesion and easy control, and skip complex circumstances such as compaction, pore water pressure, water content, seepage. The qualitative description of erosion processes, tension cracks occur, and mass movements can be characterized through the operation of model test experiments and PIV. Using PFC3D as numerical method to verify the observation in model tests.