This study investigated landslide at the site of Ruei-Li village, Meishan Township, Chiayi County. In recent years, this area faces with landslide disasters during heavy rainfalls. Particularly in August 2009, a landslide caused by Typhoon Morakot was the most serious than ever. The initial estimation of the head surface sliding body was about 1- to 2-meter drops.
The range of the sliding area is about 1000m from south to north and 450m from east to west, with 40ha area. Terrain feature is that north-side higher than south-side. It is decreasing from EL.1,115m to EL.830m of elevation ,therefore the height difference is about 285m.Mainly conservations are stores and households along the County Highway No.166 on 78K~82K.There are 8 boreholes of 40m~52m depth as observation for groundwater level and inclinometers ,and installed 15 drilled shafts in slope.
The research area belongs to Pliocene Cholan Formation formed of fine-grain and sandstone-shale. he formation attitude trends in the northeast-southwest direction closed to the geological structure. Therefore, it is formed to dip-slope. The research area divided into two parts by Haituron-River, therefore considering terrain and formation attitude, There is a good possibility of scouring at toes of slope lead to slope failure in lack of lateral bracing
From preliminary geological investigations, groundwater monitoring and other relative examinations, we found that study area is an old landslide area. Previous geological disasters have led to large-scale landslides along the body, and left in the thick layer of colluvial soils. This area is high potential in risk analysis. It recommends that for places with existing observation holes, maintain the efforts so as to achieve the desired functionality of pre-warning. In educational promotion, when typhoon strikes with dramatic rainfall, it can evacuate the public to refuge to ensure the safeties for resident lives and properties.