Study on the mechanism and prediction of debris slides

研究成果包括以下四个部分。泥石流特征：泥石流发生在斜坡上的O级盆地中，山体起伏小，基岩易风化或低固结。利用土体的导水率、抗剪强度、N值和硬度的垂直变化以及土体的根部加固，阐明了易受泥石流影响的坡面特征。土壤碎屑和饱和蚀变流：在古生界、花岗岩和第三系三个斜坡上，测量了作为泥石流潜在土层的表层土壤深度。结果是用坡度表示的。通过等高线曲率的变化，研究了O级盆地的地形发育过程。利用张力计和压力计对坡面雨水入渗过程进行了测量。利用水头图进行了分析，重建了一个典型的上新世零级盆地的地下水流模式。土壤中的管道分为两类：可见的和不可见的。此外，还讨论了管道在土壤暴雨流中的作用。随着采样圆柱体尺寸的增大，表层土壤饱和导水率的变化变小。影响滑坡发生的因素分析：收集了57个不同地区暴雨滑坡的多变分析结果。分析表明，海拔高度的重要性与其他各种因素密切相关。900米是一条分界线，海拔高于900米是最重要的，海拔低于900米是植被最重要的。树根对边坡稳定性的影响：采用无限坡度模型和上限模型估算树根加固土体的强度。从不同的角度对结果进行了讨论。

The result of research consists of the following four parts. The characteristics of debris slides: Debris slides occur in O order basins on slopes where mountain reliefs are small and bed rocks are subject to weathering or lowly consolidated. The characteristic of slope profiles vulnerable to debris slides is clarified by using the vertical variation of hydraulic conductivity, shear strength, N values and hardness of soil and reinforcement of soil by roots. Soil lapths and saturated alteral flow: Surface soil depths as a potential soil layer of debris slides were measured on three slopes, paleozoic, granite and tertiary. The results are expressed in terms of slope gradients. The process of topographical development of a O order basin is investigated with the change of curvetures of contour lines. The infiltrating process of storm water was measured on a slope with tensiometers and piezometers. Analysis was conducted with hydraulic headmaps, reconstructing subsurface flow patterns on a typical Pliocene zero order basin. Pipes in soil are classified into two catgories: visible and invisible. In addition, the role of pipes for stormflow in soil is discussed. The variation of saturated hydraulic conductivity of surface soil becomes smaller as the size of a sammpling cylinder become larger. The best size for practical use is 15-20 cm in diameter.Analysis of factors affecting landslide occurrence: Fifty seven results of multivariation analysis of landslides in a heavy storm in various regions were collected and analysed. The analysis showed the importance of altitude which is closely related to various other factors. A dividing line is set at 900 m, above which altitude is most important and below which vegetation become most important. Effect of tree roots on slope stability: An infinite slope model andan upper bound model were applied to estimate the reinforcement of soil strength by tree roots. The result is discussed from various viewpoints.