| Abstract: | 本研究主要針對現地五節芒進行採樣，輔助影像分析技術以得到芒草外觀基本資料(如株高、莖徑、根長等)，並利用碎形觀念計算根系分佈之複雜度(Db)及利用盒維度求出根系各不同深度斷面的盒維度Db(A)。另一方面，進行根繫土壤之室內直剪試驗，以求知五節芒根系複雜度與根系補強之土壤強度之增加量關係，並考慮增強的凝聚力Δc探討植生改善邊坡土壤參數，配合Stabl程式分析邊坡安全係數之改變。研究結果得致以下幾點結論：
(1)芒草根系分佈幾何確實具有碎形特色，室內分析樣本雖經擾動後但不影響總根量及其碎形參數，任一方位根系投影Db幾乎相同，且複雜度仍可逼近現地根系碎形狀況。
(2) 坡頂或坡面雖根系的生長方向不同，但株高(H)與根系分佈複雜度皆有正相關關係，雖種植區域不同但其根系碎形特色一樣。本研究植株高度10cm~134.5cm的根系分佈其Db值結果介於1.0~1.55間。
(3) 株高愈長，底部的根系規模越大且分佈越複雜。株高與根系含量呈正相關關係，且在地下0-5cm間的根斷面的Db(A)為最大，表示這段區域的根系最為複雜，所提供的根繫作用最大。
(4) 根繫作用主要在提升土壤凝聚力Δc，對摩擦角的改變不大，並隨著株高愈高凝聚力增量Δc愈多，且伴隨著根系成長，加勁改良範圍隨之擴大，所以利用植生護坡根系複雜的網結性以及根系成長擴大加勁範圍確可收穩定邊坡之效。
(5) 植生於非凝聚性土壤邊坡(凝聚力c=0)，其植生效益優於凝聚性土壤邊坡(c≠0)，並且隨著芒草株高之成長而增加抗剪強度，邊坡之安全係數也會相對提高。
In the light of Miscanthus Floridulus, this study undertakes sampling in the field and portrait analysis as auxiliary and obtains basic data of appearance of Miscanthus Floridulus; such as: shoot height, stem diameter, root length and so on. Also, making use of fractal concept to calculate complexity (Db) of root distribution; as well as using box dimension to find out different depth cross section of box dimension Db(A). At the another aspect, laboratory direct shear test of root-connected soil has been undertaken to seek for relations of Miscanthus Floridulus complexity and soil strength increase of root. Also, enhancement of cohesion (Δc) has been considered to confer slope side soil parameter of vegetation improvement; and to harmony with Stabl to analyze changes of slope side safety factor. Conclusions are listed below:
(1) The geometry distribution of Miscanthus Floridulus
actually has fractal character. Although laboratory analysis after being disturbed, total capacity of root and its fractal parameter are not influenced. And, Db of root projection of any location is almost same and complexity still closes to root fractal situation in the field.
(2) Although different growth direction of upper slope surface or slope face, shoot height (H) and root distribution complexity have positive correlation. Different root area but its root fractal character is same. The root distribution of shoot height 10cm-134.5cm, its Db value is between 1.0-1.55.
(3) The longer of the shoot height(H), the larger scope of the root bottom and its distribution is more complicated. Therefore, shoot height and capacity of root have positive correlation. When the largest of cross section Db(A) of underground 0-5cm shoot, it is meant that root in this area is the most complicated and the largest function of root-connected are provided.
(4) The main function of root-connected is to promote soil cohesion (Δc), no bigger change to friction angle. To comply with the higher of shoot height, the more of cohesion increasement (Δc) will be. It will go along with root growth and enlarge improvement. Therefore, making use of complicated knot of vegetation slope protection and enlargement of root growth, no doubt, the effect of slope side will be stabilized.
(5) When vegetation at the slope side of cohesionless soil (c=0), its effect is better than that of cohesive soil (c≠0). To follow growth of shoot height of Mmiscanthus Floridulus to increase shear strength, the safety factor of slope side will be comparatively risen. |
