不同根系植被加勁之砂性邊坡穩定性分析｜國立中央大學博碩士論文系統

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研究生：	羅伊妲 Ida Agustin Nomleni
論文名稱：	不同根系植被加勁之砂性邊坡穩定性分析 The Stability Analysis of Sandy Soil Slope Reinforcement by Different Root Types
指導教授：	洪汶宜 Wen-Yi Hung
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 土木工程學系 Department of Civil Engineering
論文出版年：	2021
畢業學年度：	109
語文別：	英文
論文頁數：	184
中文關鍵詞：	動態條件、根系加勁系統、離心模型試驗
外文關鍵詞：	centrifuge modeling, dynamic condition, root-reinforcement system
相關次數：	點閱：10 下載：0
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山坡地滑為山區常見的災難之一，山坡地的地質條件、水文環境和人為因素皆會影響邊坡的穩定性。利用植被的根系加勁可提高邊坡穩定性，根系加勁系統的優點為：透過植物的蒸散作用吸收根系周圍土壤之水分，進而使土壤產生基質吸力，增加土壤強度；加勁表層土壤抵抗表面侵蝕；增加根系周圍土壤的圍束力。
本研究使用中央大學地工離心機進行一系列之離心模型試驗，探討在靜態或動態條件下不同根系對邊坡穩定性及破壞機制的影響。邊坡模型高度為 200 mm，坡度為 45 度，土壤單位重為 14.95 kN/m3，含水量為 10%。本研究選擇三種不同根系的植物，分別為小麥草（鬚根植物）、紅豆（淺根植物）及向日葵（軸根植物）。試驗前，所有植物皆在模型邊坡上養護7天。
試驗結果顯示：（1）根系加勁系統會降低土壤的滲透性，但土壤的抗剪強度則無明顯提高，凝聚力增加約 3 kPa，內摩擦角增加約 4 度；（2）與未植生邊坡模型相比，根系加勁系統有效地提高邊坡穩定性，植生邊坡的臨界坡高更高，其中，鬚根型根系是提高砂土坡穩定性的效果最佳；（3）鬚根型根系加勁之邊坡在受最大基盤加速度為0.15 g 的振動時也能有效地穩定砂性邊坡，因為鬚根型根系能擴散到更深層的土壤。在受振條件下，鬚根型根系可減少30% 的滑動面積；（4）根據滑動土與堆積土的水平位移對坡高正規化之結果，有根系加勁之邊坡之水平位移量較小；（5）當邊坡受到最大基盤加速度為0.30 g的振動時，未植生邊坡模型的主崩陷崖之面積更廣且深度更深。

Landslides are a catastrophic event that often occurs in the world. Landslides can be induced by several factors, including geological factors, hydrological factors, and human intervention. Root reinforcement is an effective and useful solution to increase slope stability. The root-reinforcement system on the slope has several benefits: reducing evaporation, increasing soil suction by root uptake and transpiration, mechanical reinforcement by roots, erosion control, and restrain caused by the interaction between the roots system and the surrounding soil.
A series of centrifuge tests have been performed using National Central University geotechnical centrifuge research facilities to evaluate the impact of static and dynamic conditions on the stability of the root-reinforced slope and evaluate the different types of roots and their distribution to the slope failure mechanism. Wheatgrass, red bean, and sunflower are selected in this research based on the type of soil, environment, and the type of root system. A 45 degrees slope with 200 mm in height is modeled in this study. The slope is made out of 50% dry relative density, which corresponds to 14.95 kN/m3 of unit weight and mixed with 10% water content. These plants were only grown on the slope face with seven days of growing time.
From this research, it can be concluded that (1) the root-reinforcement system in the soil will reduce the soil’s permeability and insignificantly enhance the shear strength of the soil. In this study, cohesion is increased by about 3 kPa, and friction angle is increased by about 4 degrees, (2) the root-reinforcement system effectively improves slope stability which is shown by the higher critical slope height compared to the bare soil model. The fibrous root type is the most effective root system to improve sandy slope stability, (3) the fibrous root type also effectively stabilizes the sandy slope when subjected to dynamic conditions (PBA ≒ 0.15g) because the vegetation’s roots spread to a deeper layer and interconnect with other roots. In this condition, the fibrous root type can reduce the sliding area by about 30%, (4) the root reinforcement on the slope can prevent large horizontal movement after the dynamic condition (PBA ≒ 0.30g). This was proven by the smaller normalized horizontal movement of depletion and accumulation of root reinforcement slope compared to the bare soil slope counterpart after being subjected to the same input motion, and (5) during dynamic condition with PBA ≒ 0.30g, the bare soil slope has a more profound and more extensive area of the main scarp than slope with root reinforcement systems.

CHINESE ABSTRACT                                          vi
ENGLISH ABSTRACT                                         vii
ACKNOWLEDGEMENTS                                        viii
TABLE OF CONTENTS                                         ix
LIST OF FIGURES                                           xi
LIST OF TABLES                                         xviii
EXPLANATION OF SYMBOLS                                    xx
CHAPTER 1 INTRODUCTION                                     1
1-1    Research motivation                                 1
1-2    Aim of research                                     5
1-3    Content of research                                 5
CHAPTER 2 LITERATURE REVIEW                                7
2-1     Basic concept                                      7
2-1-1 Landslide                                            7
2-1-2 Root-reinforcement system on slope                   8
2-1-3 Soil-root reinforcement model                       10
2-1-4 Root area ratio (RAR)                               13
2-1-5 Newmark's sliding block analysis                    13
2-1-6 Arias intensity and cumulative absolute velocity    15
2-1-7 Predominant frequency                               16
2-1-8 Sliding area ratio                                  17
2-1-9 Earthquake intensity and the Modified Mercalli Intensity (MMI)                                           17
2-2     Centrifuge modeling                               20
2-3     Previous studies                                  21
CHAPTER 3 TESTING APPARATUSES AND MATERIAL                27
3-1     Testing apparatuses                               27
3-1-1 Element tests                                       27
3-1-2 Centrifuge test                                     29
3-2     Material                                          36
3-2-1 Soil properties                                     36
3-2-2 Vegetation properties                               39
CHAPTER 4 EXPERIMENTAL PROGRAM, RESULT, AND DISCUSSIONS   41
4-1     Element tests                                     41
4-2     Centrifuge modeling test                          45
4-2-1 Test configuration and test planning                45
4-2-2 The process of making and testing slope using a centrifuge                                                46
4-2-3 Gravity condition                                   50
4-2-4 Dynamic condition                                   67
4-3     Discussions                                      135
4-3-1 Gravity condition                                  135
4-3-2 Dynamic condition (PBA ≒ 0.15g)                   141
4-3-3 Dynamic condition (PBA ≒ 0.30g)                   147
4-4    Performance prediction of slope under dynamic condition                                                154
CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS                157
5-1     Conclusions                                      157
5-2     Future work                                      157
5-3     Recommendations                                  158
BIBLIOGRAPHY                                             159

                                

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