Assessment of Rainfall Induced Landslide Potential

• Main Authors: Lin-Bin Chiou, 邱琳濱
• Other Authors: Gwo-Fong Lin
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/96275923515198497299

博士 === 臺灣大學 === 土木工程學研究所 === 98 === The pore pressure increases due to rainfall infiltration, which may result in the slope instability. Thus, the rainfall-induced landslide is closely related to the hydrological response. Regarding the slope stability analysis in the mountain area, usually numerical models were developed and then case studies of disasters were performed. It lacked field testing, monitoring and analysis, and hence the actual hydrogeological parameters could not be integrated into the numerical models. The purpose of this study is to further understand the mechanism of rainfall-induced landslides, the influences of hydrogeological and rainfall characteristics on landslides are investigated. Therefore, instruments are installed, groundwater levels are observed, and field parameters are analyzed. These field data are integrated into the model. First, a series of field hydrogeological tests including the ground resistivity image profiling, the double-ring infiltration test, the borehole camera investigation and the double-packer test are performed to obtain the strata distribution, slip mode and hydrological parameters to help develop the hydrogeological conceptual model. Furthermore, the hydrogeological parameters and the long-term hydrological records are compiled with the GeoStudio software to perform the transient coupled analysis. The conceptual model and the corresponding parameters applied in the model are based on a series of in-situ investigations and laboratory experiments. A seepage analysis is conducted, and the model is calibrated and verified using the field monitoring data in order to investigate the relationship between landslides and hydrogeology and to understand the influence of hydrogeological characteristics on landslides. In order to understand the stability of landslide sites under different rainfall characteristics, three types of deign rainfall conditions including different patterns, intensity and cumulative amount are introduced into the model. The design rainfalls are obtained based on the data of a rain gauge near the landslide site. The coupled stability analysis is then conducted to establish the relationship between the rainfall characteristics and the slope stability. The advanced rainfall pattern has the least influence on the factor of safety while the delayed rainfall pattern has the greatest influence. It can be concluded that the delayed rainfall pattern threatens the slope stability the most among all the rainfall patterns. As to the influence of the rainfall intensity, the factor of safety decreases as the rainfall intensity increases. When the rainfall intensity is more than a threshold value, apparent decrease in factor of safety is found. Most noticeably, the factor of safety yields a significant drop when the rainfall intensity reaches a certain high value, and the drop slows down when the intensity is over that high value. It shows that the influence of rainfall intensity on the slope stability has an upper limit. Finally, as to the influence of cumulative rainfall, the factor of safety linearly decreases with increasing cumulative rainfall, but the decreasing trend is not significant.