山黃麻根系對其土／根系統抗剪強度增量之影響評估

Evaluation of the Shear Strength Increment of Trema orientalis Soil/Root System due to Roots

10.29417/JCSWC.201203_43(1).0004

林信輝(Shin-Hwei Lin)；許涵硯(Han-Yan Hsu)；劉文宗(Wen-Tsung Liu)；林德貴(Der-Guay Lin)

土／根系統 ； 極限拉拔抗力 ； 根系抗剪強度增量 ； Soil/root system ； ultimate pull-out resistance ； shear strength increment due to roots

中華水土保持學報

43卷1期（2012 / 03 / 01）

41 - 54

繁體中文

本研究採用數值方法來建立土／根系統極限拉拔抗力與其抗剪強度增量之轉換機制，以便在未來能運用於含根邊坡之穩定分析上。首先，針對台灣坡地先驅優勢植物山黃麻進行根系調查、單根抗拉強度試驗及現地根系之拉拔抗力試驗。依據調查之根系形態以及根系材料強度，吾人可建構二維之土／根系統數值模型，並用來模擬土／根系統之極限拉拔抗力P(下標 u)，以及直接剪力試驗中由於根系所提供之額外抗剪強度增量△S(下標 r)。最後，並提出△S(下標 r)=f (P(下標 u之)) 之關係轉換函數。

A mechanical conversion model was developed using a numerical method to correlate the shear strength increment due to root, ΔS(subscript r), with ultimate pull-out resistance, P(subscript u), of the soil/root system. The conversion model can be applied to determine the required shear strength parameters for stability analyses of vegetated slopes. Trema orientalis (L.) Blume (India charcoal trema), a pioneer and dominant tree on the low slopeland of Taiwan, was selected as the target species of the study for the field investigation of root morphology, in-situ pull-out tests, and laboratory tensile strength tests. Using the root morphology and the strength parameters of the root material, one can develop a 2-D numerical model of the soil/root system to simulate ultimate pull-out resistance, P(subscript u), from the pull-out test and the shear strength increment due to roots, ΔSr, of the soil/root system from direct shear tests. Eventually, a relationship function, ΔS(subscript r)=f (P(subscript u)) can be proposed for practical use.