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

通常认为，森林根系对滑坡稳定性的抵抗是由坡体纵断面上的桩作用和网络作用共同作用的。在土层与基岩的垂直连接中考虑了桩的作用，在根块之间的水平连接中考虑了网络的作用，但由于本研究的结果，我们认识到在厚土层覆盖的正常坡面上，大部分垂直根系不能到达基岩，大部分水平根块不能相互连接，这意味着在边坡的二维剖面上，根系的阻力不起垂直作用。因此，在滑坡发生的稳定性分析中，我们不得不重新考虑另一种机制。经过一些试验，我们认识到，在倾斜的土体中，在超摩擦角状态下潜伏着一种拱形结构，而根系块增加了拱形结构的抗压能力。

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.