中滑移速度下高嶺石的製動效果（速度強化）;Braking effect (velocity- strengthening) of Kaolinite under intermediate slip velocities

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Title:	中滑移速度下高嶺石的製動效果（速度強化）;Braking effect (velocity- strengthening) of Kaolinite under intermediate slip velocities
Authors:	陳愛美;Khoa, Tran Huynh
Contributors:	應用地質研究所
Keywords:	速度強化摩擦;爬行滑坡;高嶺石;速度相關的摩擦模型;velocity-strengthening friction;Creeping landslides;Kaolinite;Velocity-dependent friction model
Date:	2022-09-28
Issue Date:	2022-10-04 12:22:35 (UTC+8)
Publisher:	國立中央大學
Abstract:	摘要根據岩石力學理論，摩擦阻止滑動塊移動。此外，滑移速度影響摩擦強度。許多研究集中在界面的摩擦阻力減小而滑動速率增加。對於摩擦事件的許多要素，例如界面破裂前沿傳播的速度和它們釋放的儲存能量的數量，速度強化摩擦的重要性在很大程度上被忽視了。在中等滑移速度（10^(-7) to 1 m/s）下，通過低到高速旋轉剪切裝置對樣品進行一系列實驗，正應力為 1 MPa。本論文對剪切樣品進行了兩種不同的條件：恆速和速度步長。本研究表明，速度階躍樣品的穩態摩擦係數低於等速樣品的穩態摩擦係數。本研究結果與以往研究結果相比，穩態摩擦係數的標準偏差較大。本研究基於真實滑坡材料和純高嶺石的穩態摩擦係數結果建立了速度相關的摩擦模型。結合模型和摩擦係數只增不減的情況，即使移動體停止，本研究分析了爬行滑坡對平行滲流無限邊坡穩定性的影響。雖然真實滑坡材料和純高嶺石的摩擦強度不同，但破壞面以上地下水位高度（h_w）對結果的影響是相似的。調查結果表明，h_w 顯著影響加速度、速度和位移。如果 hw > hw-critical，則斜坡將繼續滑動而不會停止，從而使地下水位始終低於 hw-critical。本論文考慮了兩種情況： 1）如果同一個模型，最大加速度和最大速度增加，特別是隨著滑動質量的位移顯著增加； 2) 如果相同的 hw： a) 對於真正的滑坡材料，從 Model D-1 到 Model D-4（Ferri 等人，2011）以及從 Model W-5 到 Model W，最大加速度、速度和位移更大-8 純高嶺石，b) 地下水位達到峰值的持續時間越快，最大速度越高，累積位移越小。使用 Newmark 方法可以在不同情況下建立 hw 和摩擦係數之間的關係，例如斜坡幾何形狀和材料。從而設定滑坡預警閾值來評估邊坡的不穩定性。;According to the rock mechanics theory, friction prevents the sliding mass moving. Furthermore, the slip velocity affectes the friction strength. A lot of research concentrate on the frictional resistance of the interfaces decreasing while the sliding rates increase. The importance of velocity-strengthening friction for numerous elements of frictional events, such as the speed of interfacial rupture fronts propagating and the quantity of stored energy released by them, has gone largely unnoticed. A series of experiments are carried out under intermediate slip velocities (10−7 to 1 m/s) on a sample via low to high-velocity rotary shear apparatus with the normal stress of 1 MPa. This thesis conducts two different conditions for shear samples: constant velocity and velocity-step. This study shows that the steady-state friction coefficient of velocity-step sample is lower than the one of constant velocity. Comparing the results of this study with the previous studies, the standard deviation of the steady-state friction coefficient are relatively large. This study builds velocity-dependent friction model based on the results of the steady-state friction coefficients of true landslide material and pure Kaolinite. With the combination of the model and the friction coefficient only increase without decreasing even the moving mass stops, this study analyzes the process of creeping landslides on the stability of infinite slopes with parallel seepage. Although the friction strength of true landslide material and pure Kaolinite is different, the effect of the height of water table above failure surface (hw) on results is similar. The investigation results showed that hw significantly impacts acceleration, velocity, and displacement. If hw > hw-critical, the slope will keep sliding without stopping so that keeps the groundwater table always below hw-critical. This thesis considers two cases: 1) If the same model, the maximum acceleration and velocity increase, especially with the displacement of the sliding mass significantly rising; 2) if the same hw: a) the maximum acceleration, velocity, and displacement are larger from Model D-1 to Model D-4 for true landslide material (Ferri et al., 2011) and from Model W-5 to Model W-8 for pure Kaolinite, and b) the faster the time duration to reach the peak of the groundwater table rises, the higher the maximum velocity, the accumulated displacement is smaller. Using the Newmark method it is possible to establish the relationship between hw and coefficient of friction in different cases, such as slope geometry and materials. Thereby setting a landslide warning threshold to assess the instability of the slope.
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