隨著隨山崩體積增加，山崩滑移距離愈遠，排除了受控於地形因素後，通常伴隨發生移動距離超過預期（超額移動距離，excessive travel distance）之現象。造成大型山崩超額移動距離甚遠的機制，目前仍是科學界爭論不休的議題。根據文獻資料顯示，超額移動距離與體積呈正相關，藉由蒐集山崩滑移距離與滑移深度資料，顯示兩者間之關係亦呈正相關。經由高速旋剪試驗進行岩石-岩石接觸摩擦試驗與夾泥摩擦試驗，發現氣乾砂岩試體於高速剪動下（1.3 m/s），隨正向應力愈大（0.5MPa-3MPa），尖峰（1.51-0.98）與穩態（1.12-0.42）摩擦係數即愈小，其弱化機制主要由熔融物潤滑，正向應力控制岩石熔融速率，使其在較大之正向應力可以較快產生弱化機制，正向應力控制熔融帶厚度，厚度愈厚穩態摩擦係數愈低，滑動塊體需消耗摩擦能即減少，因此塊體滑移距離增加；夾泥試驗的試驗結果亦顯示隨著正向應力增加，摩擦係數隨之減小（尖峰摩擦係數：0.69-0.35，穩態摩擦係數：0.26-0.04），但試驗結果摩擦係數遠小於岩石-岩石接觸試驗。使用實驗求得摩擦係數，模擬假設山崩滑動情形，引入岩石-岩石接觸試驗摩擦係數顯示正向應力大於1.5MPa將產生超額移動距離，超額移動距離隨正向應力增加而增加。夾泥試驗的摩擦係數皆足以讓山崩產生超額移動距離，但是滑移距離對正向應力的影響較氣乾砂岩不明顯，本研究推論，超額移動距離受山崩塊體體積影響之機制，可能部分受控於滑動面正向應力之大小外，材料特性與含水量情況亦扮演重要腳色。The run-out of large landslide increased with the increasing landslide volume. Excessive travel distance is usually observed. Researchers have been looking for mechanism of this phenomenon, and that can not completely explain this phenomenon in decades. Based on the historic cases, the excessive travel distances of the landslides are highly related to its thickness (normal stress). This study uses high-velocity rotary apparatus doing a series of shear experiments on dry rocks (sandstone) and wet gouges (bedding-parallel fault gouge), performed under normal stress of 0.5-3 MPa with slip rates of 1.3m/s. The result shows that the peak friction coefficient (sandstone: 1.51-0.98; gouge: 0.69-0.35) and the steady state friction coefficient (sandstone: 0.69-0.35; gouge: 0.26-0.04) decreased when normal stress increased. Simplified cases of simulation show that excessive travel distance increase with normal stress in sandstone and gouge experiments. When normal stress is larger than 1.5MPa, it will generate excessive travel distance in rock experiments. It’s enough to friction coefficient in all gouge experiments for generating excessive travel distance. Normal stress is not significantly affected in gouge experiments. The excessive travel distance is function of the normal stress, materials and water contain.
