Investigation and Numerical Simulation Analyses of the Landslides in Terrace Formation

Abstract

In situ exploration and sampling are carried out in Sin-San Village in Nantou County after the typhoon. Large direct shear tests in the laboratory are performed to measure the shear strength of the material. The soil water characteristic curve of the soil was derived from the pressure plate tests. The cross-section profiles of the failed slope before and after the typhoon at this area are obtained using digital elevation model (DEM) and 3D terrestrial scanner, respectively. The numerical softwares, SEEP/W and SLOPE/W, are used to analyze the slope stability under the similar rainfall by the typhoon. Different ground water level, river level, and friction angle of the soil are considered to compare the values of factor of safety and to reveal the failure processes of the slope. The possible failure of the slope may be due to scouring of the toe of the slope by the surge of rising river level and/or mud flow based on the investigated profiles and the numerical simulations. The estimated length of scouring was about 20 m long. The possible mechanism of failure for this length of scouring could be due to multiple retrogressive failures after toe scouring based on the numerical modeling.