Development of evaluation techniques of the effect of tree roots on slope stability.

点击翻译按钮获取中文摘要

1) A conceptual model which express the lateral roots with nets and vertical roots with short piles is represented. The change of the effect tree roots on slope stability is discussed with this model.2) The slope is classified into four types with the subsurface conditions into which vertical roots penetrate. It is pointed out that the slope with the transition layer which restricts tree root growth is affected greately by tree cutting.3) The pipe theory and the bifurcation ratio are employed for making a simulation model to estimate the lateral root network. The lateral roots showed the lowest volume at the middle of two adjacent trees. This lowest volume increased sharply before the tree age of 20. After 20th year, the lateral root volume showed a constant value. Since this 20 years correspond to the high occurrance period of debris slides after tree cutting, the writer presumes that lateral roots affect slope stability.greatly.4)The upper bound theorem is applied to evaluate the effect of lateral roots and vertical roots simultaniously. The result showed that the effect of lateral root becomes greater as the landslide becomes smaller. The effect of vertical roots becomes greater as the surface soil depth gets smaller.5) The relationship between four slope types and the effect of tree roots on slope stability is classified and evaluated with the aid of the upper bound theorem taking into consideration the surface soil depth and the growth restriction of vertical roots.