Construction of forest root system and its function to stability of landslide on mountainous slope.

一般认为，林木根系对滑坡稳定性的抵抗作用是桩作用和坡面纵向网络作用共同作用的结果。在土层与基岩的竖向联系中考虑桩的作用，在水平方向上考虑根块之间的网络作用，但由于本研究的结果，发现在厚土层覆盖的正常边坡中，垂直根系大多数不到达基岩，水平根块大多数不相互连接，这一结果表明，在斜坡的二维剖面中不垂直。因此，在滑坡发生的稳定性分析中必须重新考虑另一种机理，通过试验认识到，在斜坡土体中，在过摩擦角的状态下，潜在地形成一种拱结构，根系块体增加了拱结构的抗压能力。

Usually, we have considered that resistance of forest root system to stability of landslide is done by both functions pile action and net-work in longitudinal section of the slope. Pile action is considered in vertical connection between soil layer and bed rock, net-work is considered in horizontal connection of root blocks with each other.But, as a result of this study, we recognized both phenomena that most of vertical root system does not reach to bed rock and most of horizontal root blocks do not connect each others in normal slope covered with thick soil layer.This result means that resistance of root system does not work vertically in the 2-dimensional section of slope. Therefore, we have to consider newly another mechanism in the stability analysis to landslide occurrence.After some experiments, we have recognized that one kind of arch structure are formed latently in the sloped soil body on the state of over friction angle, and root system blocks increase resistance to compression of arch structure.