Study on the mechanism and prediction of debris slides

研究结果包括以下四个部分。碎屑滑坡特征：碎屑滑坡多发生在坡度较小、基岩风化或固结程度较低的斜坡上的O级盆地。利用土体的导水系数、抗剪强度、N值、硬度的垂直变化规律和根系对土体的加固作用，阐明了边坡易发生泥石流的特征。土壤层与饱和交替流：在古生代、花岗岩和第三系三个斜坡上测量了地表土壤深度作为潜在的碎屑滑坡土层。结果用坡度表示。利用等高线曲率的变化研究了O级盆地的地形发育过程。用张力计和压电计测量了暴雨在斜坡上的入渗过程。利用水力水头图进行分析，重建了上新世典型零级盆地的地下水流模式。土壤中的管道分为可见和不可见两类。此外，本文还讨论了管道对土壤中暴雨流的作用。随着采样筒尺寸的增大，表层土壤饱和水导率的变化越小。实际使用的最佳尺寸是直径15-20厘米。滑坡发生的影响因素分析：收集了某次特大暴雨地区滑坡多变分析的57个结果，并进行了分析。分析表明，海拔的重要性与其他各种因素密切相关。在海拔900米处有一条分界线，海拔900米以上最重要，海拔900米以下植被最重要。树根对边坡稳定性的影响：采用无限边坡模型和上限模型估计树根对土体的加固强度。结果从不同的角度进行了讨论。

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.