樹根力與坡面穩定關係之研究

THE RELATIONSHIP BETWEEN THE TREE ROOT STRENGTH AND THE SLOPE STABILITY

吳正雄(Jenug Hsiung Wu)

《中華水土保持學報》 24卷2期 (1993/11) Pp. 23-37

https://doi.org/10.29417/JCSWC.199311_24(2).0003

摘要

森林提供坡面穩定的功能，主要來自於蒸散作用而調節土壤水分的機能，以及根系補強力量所提供的根力效果。根系補強力量則由於根株的機械補強力量以及根與土壤的緊縛力量所發揮的結果。本研究爲探討森林防止崩塌的功能，檢討根力模式的適用性，經選定臺灣杉、臺灣赤楊以及山黃麻於蓮華池、溪頭、林口等地的不同土壤環境下，進行根系調査、根拉力試驗以及野外含根土壤直接剪力試驗，藉以推估不同樹種之根力作用以及對安全因數之影響。經研究結果各供試樹種之根拉力強度與根直徑成指數廻歸關係，根拉力強度得以推估含根土壤之剪力強度增量。由於根的存在而使土壤剪力強度增加150〜730kg / m^2，增加率由15.4〜50.4％，且土壤剪力強度因根斷面積增加而增加。以無限坡面分析法分析結果，於蓮華池坋質黏土之臺灣杉林地及林口臺地礫石層之山黃麻林地，含根土壤因根力作用而有效提高安全因數F值增加率爲16及35％，而有助於淺層崩塌抑制之功能。

關鍵字

根力 ； 根拉力強度 ； 坡面安定分析

並列摘要

Forest vegetation provides function for improving the stability of slopeland by means of adjusting the storage of soil water through the operation of transpiration and reinforcing the resistance to slide due to the increase of land force between soil and roots. In this study, Taiwan cryptomerioides, Alnus formosana and Trema orientalis were selected to study the preventive function of forest to shallow landslides and the feasibility of current moods for estimating root strength. Through the investigations of root system, tests of root tensile- strength and experiments of shear strength by in-situ direct shear tester, the root strength for different species and its effect to safety factor were evaluated. The results were got. The tensile strength of root was proportional to its diameter exponentially. And, the root strength cauld be estimated tensile strenth of root. Because of the existence of root, the shear strength of soil was increased rate from 15.4 to 50.4%. And, the increase of root area, the increase of the shear strength of soil. By using the analysis model of infinite slope at Lien-Hua-Chih and Lin-Kou areas, result showed that the safety factor, F, was significantly increased for increase of root strength of soil. The F-values of taiwania and trema were, in comparison with the area without roots, increased by 16 and 35%, respectively, and cauld contribute to prevent the shallow landslides.

並列關鍵字

Root Strength ； Tensile Strength of Root ； Slope Stability Analysis