Investigation on Failure of Slopes along Mileage 33Km of County Road 149A due to Typhoon Sinlaku of 2008

• Main Authors: Yuan-Hong Lan, 籃元宏
• Other Authors: Muhsiung Chang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/33005403500972122338

碩士 === 國立雲林科技大學 === 營建工程系 === 102 === County Road 149A is a main route to Tsaoling Scenic Area in Yunlin County. The entire roadway has been suffered frequent damages as a result of landslips or slope failures during typhoon or rainstorm seasons. After the 921 Chi-Chi earthquake in 1992, the slope along Mileage 33K of the road has been loosen and become unstable. The aim of this study was to understand the cause of the failure of slope along Mileage 33K of County Road 149A due to Typhoon Sinlaku of 2008. National Yunlin University of Science and Technology (NYUST) conducted a on-site investigation and monitoring program in the study area in early of 2011. The monitoring data included surface and subsurface deformations, rainfall, and groundwater levels, which were then used to analyze the influence of rainfall on groundwater fluctuation and subsurface deformation. This study also performed numerical simulations to calibrate hydraulic conductivity of the colluvium for the seepage analysis. According, we were able to analyze the groundwater table and stability of slope during Typhoon Sinlaku of 2008. Based on our monitoring and simulation results, the slip surfaces of the 2008 failure were located at 20-50 m below the ground surface. The displacement of the slope was affected by the rainfall and the erosion of slope by Shimankeng river. The simulation results showed groundwater flowed down the slope along the shale stratum and landslide occurred along this interface. The factor of safety against slope failure would be less than 1 with high rainfall and groundwater table that occurred in Typhoon Sinlaku of 2008. The simulation results are consistent with the observations of in-situ. Finally, we conclude this study that the heavy rainfall and substantial groundwater response were the main causes for the failure of the slope along Mileage 33Km of County Road 149A during Typhoon Sinlaku in September 2008.