Effects of Rainfall Infiltration on Slope Stability

• Main Authors: Hsu, Chung-Li, 許中立
• Other Authors: Hao-Jung Shieh
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/4x49g2

博士 === 國立中興大學 === 水土保持學系 === 86 === Taiwan, located in the mobile belt of the eastern side of Asia, is highly susceptible to hillslope movements as a result of contributing factors such astopography, geology, earthquate, typhoon and heavy rainfall. In recent years,hillslope landuse changes and development activities often increase the severity of sediment related disasters, resulting in great loss of properties and lives. Consequently, in-depth studies on landslide mechanisms and protection measures are very important research topics. However, factors contributing to landslides are complex. These include weak stratum structure and the abnormal hydrologic and hydraulic conditions. Majority of landslides are caused by raised groundwater table due to great amount of precipitation. The purpose of this study was to investigate rainfall infiltration and groundwater table changes on slope stability with data from field observations and theoretical analyses based on the principle of soil mechanics and hillslope hydrology. The results will help understand the influences on slope stability by characteristic of rainfall infiltration, groundwater table raising, as well as movement of soil water and groundwater. The study results show that in addition to the undercutting of slope by gully and headward erosion, reduced soil strength due to high groundwater table by rainfall infiltrationcan result in the slope sliding. The strain magnitude (the earth stress), groundwater table and soil hydraulic conductivity are significantly affected by the precipitation and antcedent soil water content. The response range of underground strain magnitude is positively related to the increasing precipitation. This responses generally occur several days later, depending on antcedent soil water content. Groundwater table rising have a lag time of about several hours to one or two days and the recession times are about three or four days. The response rangeof decreased soil water content and increased lag time are dependent on depth in the soil profile. Statistical method is used to determine the sampling size by allowing index values of confident limit and relative error. The combined use of infiltration model and saturate- unsaturate soil water transporation model for the slope stability evaluation give results that closely conform with field observations.