地形劇烈變化河道之沖蝕特性及其對河道穩定性的影響及治理策略-子計畫:多重物理融合量測於岩石河床材料本質抗沖蝕性探討(I)

Abstract

由於臺灣獨特之氣候與地質地形條件，造成岩石質河床沖蝕或下切所延伸之工程行為影響，甚至人命財產損耗，為目前國內產學界主要關注課題。有鑑於此，前期研究針對於岩石河床的沖蝕機制、沖蝕模式與沖蝕影響等，已初步提供相關課題探討。現有研究成果顯示，岩石河床之抗沖蝕能力為一重要指標參數，可提供沖蝕率以及沖蝕模式建立與率定使用。其中常用為抗沖蝕指數(erodibility index, Kh)，主要考量材料強度、顆粒/塊體尺寸、弱面/顆粒間抗剪強度，以及地盤構造條件等因子，藉以評估沖蝕發生與否。 然而上述材料強度因子評估方法，大多利用現地史密特錘或是取樣進行單壓強度，以做材料強度評分，對於可能之材料本體膠結(cohesion)程度或內部孔洞(pore)或微細裂隙(fissure)影響，甚至於材料內部弱化、內部損傷、或疲勞效應等特性描述，不易以史密特錘或單壓強度等綜合性強度指標概括之。因此本研究擬定提出多重物理融合(multi-physics fusion )量測概念，包含利用電學、震波以及熱導等基本物理量測方法。初步規劃由室內進行相關方法評析以及感測元件研發，再配合其他子計畫之物模試驗測試驗證，藉以提供材料沖蝕關連性初步歸納與探討。最後結合現場觀測與驗證，以做進一步岩石河床材料本體特性於抗沖蝕性評估應用。

Because of the unique characteristic of Taiwan geology and whether condition, continuous terrain variation in the main channel due to rapid bedrock erosion could be a great threat to the function and the safety of cross-river infrastructures, as well as ecology sustainability of the river system. Appropriative countermeasure to deal with rapid bedrock erosion is essential for aforementioned problems. Previous studies have initially provided observation of the processes and the phenomena of bedrock erosion, and developed a bedrock erosion rate model. Among these, the erodibility index proposed by Annandale was adopted for characterizing the rock eroded resistance. However, the mass strength evaluation is only from the results of unconfined compression strength tests or SilverSchmidt method. The current strength evaluation does not consider the further influence factors, such as particle cohesion, internal pore and fissure of rock, even the material inner local failure, fatigue, accumulated damage, and dissipated energy, as suggested by previous studies. Therefore, this study proposes a multi-physics fusion methodology, including the electrical, seismic wave, and thermal measurement principles, to provide the correlations between these multi-physics fusion results and rock bed erodibility via laboratory physical model tests preliminarily in the first and second years tasks. Finally, the in-situ tests will be compared and verified with field monitoring results of the other collaborative sub-project. All the revealed results will be implemented into bedrock erosion rate model practically.