| 摘要: | 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. |
