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| 題名: | 台灣紅菜坪地滑區崩積層材料摩擦特性與受震運動特性分析;Frictional and kinematical characteristics of the Hungtsaiping landslide, Taiwan |
| 作者: | 陳羽甄;Chen, Yu-Chen |
| 貢獻者: | 應用地質研究所 |
| 關鍵詞: | 集集地震;紅菜坪地滑區;旋剪摩擦試驗;Newmark位移分析 |
| 日期: | 2018-07-26 |
| 上傳時間: | 2018-08-31 15:05:32 (UTC+8) |
| 出版者: | 國立中央大學 |
| 摘要: | 紅菜坪地滑區為1999年集集大地震誘發之山崩之一，其滑動範圍廣、滑動面深度深、地質構造複雜。前人曾採用多種方法探討其滑動機制及進行穩定性評估，然而，邊坡穩定性與材料強度參數、環境因素(地震、地下水等)高度相關，故本研究目的為利用低至中速(2.1×10-7 - 1.3×10-2 m/s)旋剪摩擦試驗瞭解滑移速度對其剪力強度之影響，將實驗結果結合紅菜坪地滑地周邊強震站之集集地震加速度資料，進行圓弧型滑動面之Newmark位移分析，瞭解受震後紅菜坪地滑地之運動特性，探討其滑移二、三十公尺山崩之原因。本研究試體為低塑性黏土，礦物組成中含有石英、長石及黏土礦物，黏土礦物中以伊萊石最多(41.3%)、膨潤石與混層膨脹性黏土礦物次之(36.9%)、少量高嶺石(11.3%)與綠泥石(10.5%)。旋剪摩擦試驗結果分為兩部分：(1)正常壓密、浸水條件之定速試驗穩態摩擦係數於滑移速度小於2.1×10-5 m/s時隨速度變化無明顯變化(μ=0.25-0.27)，當滑移速度於4.0×10-4至2.1×10-4 m/s之間，摩擦係數快速下降(μ=0.11-0.13)，滑移速度達1.3×10-3 m/s以上，摩擦係數更降至極低值(μ=0.02-0.03)，分階定速試驗之穩態摩擦係數於速度變化時，亦無明顯變化，取平均值μ=0.20；(2)過壓密、自然含水量條件試驗之定速穩態摩擦係數於滑移速度2.1×10-5、1.2×10-3及1.3×10-2 m/s時，摩擦係數分別為0.27、0.05及0.08，分階定速試驗結果於速度範圍2.1×10-7至2.1×10-4 m/s時是所有試驗結果中摩擦係數最高的(μ=0.36-0.41)。利用STABL 5M計算出臨界加速度與摩擦係數關係為Ac=0.63μ-0.23，以此式帶入圓弧型破壞面之Newmark位移分析中以進行紅菜坪地區之受震運動分析，分析分為兩部分：(1)若摩擦係數為定值(不隨滑移速度改變而變化)時，以TCU072測站加速度、略大於無地震、安全係數為1.0時之摩擦係數值(0.36)0.366(過壓密、自然含水條件下分階定速試驗結果之摩擦係數平均值)作為分析輸入值，分析結果顯示累積位移為24.51公尺，接近前人實測紅菜坪地區於集集地震期間地表平均水平位移24.7公尺，然而此分析結果中，塊體之最大滑移速度為0.91 m/s，達此滑移速度時不論是眾多前人研究及本研究實驗結果皆顯示摩擦係數會弱化至約0.1，進而發生快速、長距離滑動山崩事件；(2)若考量室濕條件、紅菜坪山崩材料礦物組成相似之Vajont山崩材料之速度相依摩擦律，與紅菜坪地區周圍四強震站資料進行Newmark位移分析，分析結果顯示其中三測站會發生快速、長距離滑動。根據以上兩點，推測紅菜坪坡趾處溝谷中之人工壩體為讓紅菜坪滑動塊體未發生快速、長距離滑動之重要原因。;The Hungtsaiping (HTP) landslide is a gigantic, deep-seated landslide that was triggered by 1999 Chi-Chi earthquake. In previous studies, researchers used several methods to understand the sliding mechanism and to evaluate the stability of this area. However, the most important factors of the soil slope stability analysis are strength parameters, environment conditions, and the selection of the profile to be analyzed. The objective of this study is to understand the velocity-dependent frictional characteristics through the low-to-medium shear rate (2.1×10-7 – 1.3×10-2 m/s) rotary shear tests and the kinematical characteristics during Chi-Chi earthquake by Newmark displacement analysis for circular sliding surface. Discussing the reason on the movement of 20-30 m landslide at HTP landslide area during Chi-Chi earthquake.
The rotary-shear experiment results can be divided into two part: (1) The single constant velocity rotary-shear experiments under normally-consolidated, immersed in water conditions show that frictional characteristics are velocity-neutral (friction coefficient not varied with shear velocity) at low slip rate (μ=0.25-0.27) when slip rate smaller than 2.1×10-5 m/s. When slip rate in the range 4.0×10-5 - 2.1×10-4 m/s, μ decrease rapidly (μ=0.11-0.13). When slip rate reach 1.2×10-3 m/s, μ even drop to very low value (μ=0.02-0.03). The velocity-stepping experiments indicate that when slip rate changed, the friction coefficients are velocity-independent, which with an average value of 0.20, which is comparable to the value of single constant shear velocity experiments under low slip rate. (2) The single constant velocity rotary-shear experiments under over-consolidated, natural water content conditions show that frictional coefficients are 0.27, 0.05 and 0.08 at slip rates are 2.1×10-5, 1.2×10-3 and 1.3×10-2 m/s, respectively. The friction coefficients of velocity-stepping experiment are largest in all of the shear experiments at velocity of 2.1×10-7 to 2.1×10-4 m/s (μ=0.36-0.41).
This study use STABL 5M to calculate the critical acceleration under different friction coefficient. The relation between critical acceleration and friction coefficient can express as Ac=0.63μ-0.23, which is used in Newmark displacement analysis. The analysis results have divided into two part: (1) If friction coefficient is 0.366 (the average μ of over-consolidated, natural water content velocity-stepping experiment), that slightly higher than the friction coefficient, 0.36 (the μ when F.S equal to 1.0 without earthquake occurrence), the Newmark displacement analysis yields a result that closest to the reality measured average horizontal displacement, 24.7 m. However, the maximum slip velocity calculated by Newmark displacement analysis during earthquake almost reach 1.0 m/s. At this velocity level, steady-state friction coefficient will weaken to about 0.1 in previous studies and this study. Once the friction coefficient weakens to 0.1, the HTP landslide won’t stop. (2) This study incorporated velocity-dependent friction law of Vajont landslide gouges (mineral composition similar with HTP landslide gouges) under room-humidity condition with Newmark displacement analysis. Three of four strong motion stations’ analysis results show that HTP area also have rapid, long distance landslide occurred. According to the aforementioned, we speculate that the resistance force contributed by the artificial structures at toe of HTP landslide area is the important reason to stop the rapid movement of HTP landslide. |
| 顯示於類別: | [應用地質研究所] 博碩士論文
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