生態工程中植生根系對飽和－未飽和邊坡穩定影響之模式分析

Simulation of Saturated-Unsaturated Slope Stability on the Influence of Root of Plants in Ecological Engineering

馬國宸(Kuo-Chen Ma) ； 李奕達(I-Ta Lee) ； 陳主惠(Chu-Hui Chen) ； 譚義績(Yih-Chi Tan)

《農業工程學報》 52卷2期 (2006/06) Pp. 30-45

https://doi.org/10.29974/JTAE.200606.0004

摘要

植生的應用乃為生態工程當中不可或缺的重要元素，然而在邊坡穩定上植生之施工為必然的趨勢，其根系對於邊坡穩定之效益在以往許多研究中可以有相當程度的了解。但大體來說，植生對於邊坡穩定之影響不完全侷限於根系力學上，尚有許多不同的影響因子，例如：樹重、風載力、降雨截流以及土壤水份的變化等，這些都會影響植生在邊坡穩定上的結果。
本文乃利用模式分析去探討在不同坡度及土壤水份分佈之下，植生根系的存在對於邊坡穩定上實際效果。在根系力學的模式當中，本研究利用吳正雄(1990)「植生根力與坡面穩定關係之研究」中，其對台灣杉及山黃麻的根系力學所做的分析結果作為基礎，再利用Geo-Slope中的Slope/W (1991)地層及破壞面上的資料，最後經由8種不同土壤水份情況下的Bishop修正分析法及Janbu簡化分析法去分析破壞面上無植生及不同植生方式下之邊坡安全係數值。
分析結果發現，台灣杉及山黃麻於破壞面最深深度1.3m之破壞面上分別可提升安全係數0.88~1及0.77~0.93；於破壞面最深深度3.4m之破壞面上，台灣杉及山黃麻分別可提升安全係數0.05~0.13及0.04~0.12；但是，在破壞面最深深度4.9m之破壞面上，台灣杉與山黃麻之安全係數變化介於-0.01至0.05之間；然而在更深之破壞面上植生根系所能增加之安全係數皆於0.03以下，於邊坡土壤水份乾燥狀態下甚至使得安全係數降低0.017，顯示植生根系對較深破壞面上的土壤抗剪強度毫無作用，甚至會讓邊坡安全係數降低。在實際應用方面，各類植生特性必有其適合邊坡類型或坡地生態工程設計，必須經由更精準的研究分析，才能夠找出真正適用於特定邊坡上的生態工程。

關鍵字

邊坡穩定 ； 土壤水份 ； 安全係數 ； 生態工程

並列摘要

Planting is an indispensable element of ecological engineering. It is the ultimate option for slope stabilization. Past studies have shed light on the effect of the roots in steadying gradients.
This paper utilized pattern analysis to explore the impact of planting on slope stabilization under different slope grades and hydrological conditions. The mechanical model of the root system in this study is based on ”Relations of Root System Mechanics and Slope Stability” (Wu, 1990) in which he studied root system mechanics of Taiwan fir and Mountain jute. Geological layer and destruction surface data of Slope/W (1991) are then utilized. Finally through Bishop's adjusted analysis method and Janbu's simplified analysis method under 8 different soil water content conditions, slope safety coefficients of destruction surface without plant or with plants of different kinds.
The results indicated Taiwan fir and Mountain jute are capable of raising safety coefficients of destruction surface at 1.3m under from 0.88 to 1 and from 0.7 to 0.93 respectively. At the destruction surface at 3.4m under Taiwan fir and Mountain jute are capable of raising safety coefficients from 0.05 to 0.13 and from 0.04 to 0.12 respectively. At the destruction surface at 4.9m under, changes in safety coefficients caused by Taiwan fir and Mountain jute are both from -0.01 to 0.05. At deeper destruction surface increases in safety coefficient caused by planting are all below 0.03. Under lower soil water content of slope conditions, the safety coefficient is decreasing 0.017, indicating the fact that at deeper destruction surface planting does not enhance the safety coefficient and may cause it to decrease. In practice, there must be its slope type or ecology engineering design that is suitable for while planting characteristics of all kinds. Detailed study and analysis are required for identifying the suitable ecological engineering for a particular slope.

並列關鍵字

Slope stabilization ； Soil water content ； Safety coefficient ； Ecological engineering