Toward Connecting Failure Mechanism — Investigation of Precipitation Induced Mudstone Landsliding

Abstract

On September 28 2016 due to the typhoon Megi mudstone slope failed in in Yanchao district Kaohsiung city which damaged a building and buried three lives To investigate the mechanism of the rainfall-induced mudstone landsliding the field investigation was used to evaluate the geological conditions of the study area and the experiments were conducted to obtain the characteristics of geomaterials Then finite element analysis (FEA) and discrete element analysis (DEA) were employed to explore the driving mechanism in the prefailure regime and the dynamic runout process in the postfailure regime respectively In FEA the driving mechanism was revealed in terms of the pore water pressures saturations and displacement of the sliding zone The onset of the rainfall-induced landsliding was found by the rapid change of source displacement (RCSD) The result indicated that the variation of saturation and pore water pressure at the monitor points near the surface was earlier than other locations because rainfall first passes through the monitoring points near the surface; The likely failure timing was ascertained as 28 hr from the beginning of the typhoon rainfall In DEA based on the result of the FEA the estimated seepage force was obtained To account for water infiltration associated with the dynamic runout process of the landsliding and reconstruct the dynamic runout process of the landsliding the reduced sliding friction coefficient in DEA was examined Based on the results satisfactory agreement between the numerical analysis and landslide behavior was realized Water infiltration and transition in steepness play significant roles in the behavior of the dynamic runout process The landsliding exhibited a maximum speed of 4 41 m/s and decelerated as it reached a gentler slope Overall the study indicated that the combination of FEA and DEA can be utilized to investigate the failure mechanism of landslides and provide useful insights The approach can be a high potential to investigate many other geotechnical problems and help us better understand their mechanism

Date of Award	2018 Jun 26
Original language	English
Supervisor	Ching Hung (Supervisor)