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研究生:朱宗宣
研究生(外文):Tsung-Hsuan Chu
論文名稱(外文):Effect of Vegetation on The Stability of Sandy Slope by Centrifuge Modeling
指導教授:洪汶宜
指導教授(外文):Wen-Yi Hung
學位類別:碩士
校院名稱:國立中央大學
系所名稱:土木工程學系
學門:工程學門
學類:土木工程學類
論文種類:學術論文
論文出版年:2018
畢業學年度:106
語文別:英文
論文頁數:150
中文關鍵詞:離心模型試驗植生工法沖蝕邊坡穩定性
外文關鍵詞:Centrifuge modelingVegetationErosion controlSlope stability
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近年來全球暖化使環境保育及生態復育的問題越來越受到重視,台灣西部平原狹長,人口增加使山坡地的使用日漸增加,因此在山坡地工程發展許多生態工法,以期能降低人為開發對環境和生態的影響。本研究使用地工離心機暨震動台等設備進行試驗,探討邊坡植生在重力、地震力與降雨三種自然營力作用下,對緩坡抗沖蝕效能及邊坡穩定性的影響。離心模型使用小麥草模擬植物根系在邊坡中的加勁效果,試驗內容包含石英砂之基本力學性質、剪力強度、滲透係數、小麥草之基本生長特性等。最後進行離心模型試驗,以雷射掃描試驗前後坡面的位移,並以攝影機監測邊坡滑動破壞情形。
由直剪試驗的結果顯示(1) 具有根系的砂土試體內摩擦角會增加約6度,凝聚力則多了2 kPa;(2) 定水頭試驗結果顯示,根系對砂土滲透係數沒有明顯的變化,皆約為滲透係數為 7×10-5m/s;(3) 離心模型振動台試驗結果顯示,加入根系的邊坡試體在受震後之坡頂沉陷減少約50%,且坡腳堆積區坡角增加11度,砂土堆積體積範圍減少13 %。試驗後將植生與未植生邊坡模型剖面進行微型十字片剪試驗和含水量試驗,皆顯示試驗後邊坡含水量隨高度增加而遞減,邊坡表面的含水量偏低,且幾乎沒有基質吸力產生的凝聚力。根據地震力作用條件結果顯示,根系加勁試體之降伏加速度大於未根系加勁模型0.03 g,邊坡角度大於9度,植物根系有較佳的加勁效果;(4) 模擬降雨作用試驗結果顯示,無根系加勁模型之滑動速率為根系加勁模型的3.2倍,植物根系能減緩邊坡滑動發生,但根系加勁模型之破壞面較未加勁模型深,且試體之地下水位上升速度約大於2.5倍,表示植物根系能夠保護加勁範圍的淺層土壤,但雨水的入滲會引致較深層的滑動破壞。
In recent years, global warming has made an important issue of environmental conservation and ecological restoration. The western plain in Taiwan are long and narrow, and the increase of population has led to increase of using slope land. Therefore, many ecological engineering methods have been developed in slopeland. In this study, centrifuge modeling tests were evaluated the effects of slope with vegetation on the erosion resistance and slope stability under the gravity, earthquake and rainfall conditions. Wheatgrass was to be simulated the roots reinforcement in the slope by centrifuge modeling test. This study included the element tests of quartz sand, shear strength, permeability, and growth characteristics of wheatgrass. the displacement of the model before and after the centrifuge modeling tests was measured by laser displacement transduce. The failure of the slope model was captured by cameras.
The results of the direct shear test showed that (1) the friction angle of the sample with roots increased 6 degrees, and the cohesion was increased 2 kPa. (2) The test results of the constant head tests showed that the root has no obviously change of permeability. The permeability were around 7 × 10-5 m/s; (3) The centrifuge modeling tests showed the settlement on the top of slope with root reinforcement was reduced 50% after the earthquake. The slope angle of the accumulation area increased 11 degrees, and the accumulation decreased 13%. After the test, the micro torvane test and water content test were carried out with and without vegetation slope models. It showed that the water content of the slope decreased with the increase of the height After the test, the water content of the slope surface was low, and there was almost no cohesion induced by matrix suction. According to the results of earthquake conditions, the yield acceleration of the model with vegetation is greater 0.03 g than without vegetation one, and the slope angle was also greater than 9 degrees without vegetation one. The roots had effectively a reinforcement; (4) The centrifuge modeling test by rainfall condition showed that the model without vegetation is 3.2 times than that with vegetation one. The roots could buffer the slip rate but the model with vegetation has a deeper failure surface than without vegetation one and the groundwater level raised more than 2.5 times. It was indicated that the roots could effectively erosion control, but the infiltration of rainwater will cause deeper failure than without vegetation one.
CHAPTER 1 1
INTRODUCTION 1
1.1 BACKGROUND INFORMATION 1
1.2 AIMS OF RESEARCH 6
1.3 RESEARCH PROCESS 7
CHAPTER 2 9
LITERATURE REVIEW 9
2.1 SOIL PROPERTIES ON SLOPE STABILITY 9
2.1.1 Shear strength of soils 9
2.1.2 Permeability of soils 9
2.1.3 Root area ratio 10
2.1.4 Shear strength of root reinforcement soil 10
2.2 CENTRIFUGE MODELLING 11
2.2.1 The concept of centrifuge modeling 12
2.2.2 The concept of dynamic centrifuge modeling 13
2.3 RELATED STUDIES 15
2.3.1 Discussion on scaling law of rainfall condition 15
2.3.2 Reinforcement tests by centrifuge modeling 21
CHAPTER 3 24
EXPERIMENT METHOD AND EQUIPMENTS 24
3.1 EXPERIMENT METHOD 24
3.2 TEST MATERIAL 24
3.2.1 Quartz sand 24
3.2.2 Wheatgrass 27
3.3 CENTRIFUGE MODELLING TEST FACILITIES 35
3.3.1 NCU-Geotechnical centrifuge 35
3.3.2 Aluminium rigid container 35
3.3.3 Torvane 35
3.3.4 Rainfall system 36
3.3.5 Accelerometer 36
3.3.6 Pore water pressure transducer 36
3.3.7 Cameras 37
3.3.8 3D printer 37
3.3.9 Hammer 37
CHAPTER 4 47
CENTRIFUGE MODELLING AND TEST RESULTS 47
4.1 TEST PROCEDURES 47
4.1.1 The definition of quantity 47
4.1.2 Test Configuration 48
4.1.3 Model preparation 48
4.1.4 Process of centrifuge test 49
4.1.5 Test planning 49
4.2 GRAVITATIONAL CONDITION 52
4.2.1 Test – GE_80g 53
4.2.2 Test – VGE_80g 58
4.2.2 Discussions of gravitation condition 63
4.3 EARTHQUAKE CONDITION 68
4.3.1 Test – VGE_65g 69
4.3.2 Test – E_25g 74
4.3.3 Test – VE_25g 82
4.3.4 Discussions of earthquake condition 91
4.4 RAINFALL CONDITION 96
4.4.1 Test – R_25g 97
4.4.2 Test – VR_25g 104
4.4.3 Discussions of rainfall condition 113
4.5 COMPREHENSIVE DISCUSSIONS 122
CHAPTER 5 126
CONCLUSIONS 126
5.1 CONCLUSIONS 126
5.2 RECOMMENDATIONS 127
 References  129
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