| dc.description.abstract | Landslide is the primary driver of the denudational process and sediment source dominantly onsite. Landslides are one of the most disastrous effects in Taiwan; groundwater or flood erosion is highly attributed to the landslide. The slope dip angle and water-induced slope cause increased driving force and decreased resisting force, causing a slope landslide. This condition generally affects slope stability to the understanding effect of dip angle attributed to the landslide. In this study, we attempt to consider the uncertainty of the dip angle in slope stability analysis. The dip angles employed in this study were based on Highway no. 3 sliding events in Taiwan. Four different measurement sources, i.e., Central Geological Survey (C.G.S., Taiwan), Compass measurement before the sliding event, Surface measurement after the event, and LiDAR-derived data, were employed in this study.
Four methods were employed to analyze attributed dip angle to the landslide, i.e., Limit Equilibrium, monte Carlo simulation, Point estimate method (P.E.M), and 3DEC software simulation. In this research, the Monte Carlo simulation was used to quantify the effect of the geological uncertainty. Various dip angles (with mean and standard deviation) were employed to generate 100000 dip angle samples.
The limit equilibrium was used to quantify the safety factor of each measurement dip angle in the condition of no cohesion, no anchor, and no water pressure effect. The point estimate method was used to predict the probability of displacement length, displacement width, and debris volume. The point estimates method also predicts the risk of displacement length to the building in two scenarios applied. 3DEC software was used to simulate the simplified model 100m by 100m by 100m were cut off by dip angle of each measurement and various joint spacing.
Limit equilibrium results show that the LiDAR measurement source provides the highest safety factor of the slope due to the lowest dip angle. Monte Carlo simulation results show LiDAR Measurement Source provides the lowest failure probability of 16.9%, and Central Geological Survey (C.G.S., Taiwan) Measurement provides the highest failure probability of 78%. 3DEC simulation shows the effect of damping factor, dip angle, and joint spacing on the displacement length, displacement width, debris volume, and mechanical time of debris to stabilize. The point estimate method (PEM) shows that the LiDAR measurement source provides the lowest probability of 17% of the debris reaching the building at a distance of 50 meters and probability 0% of the building at a distance of 200 meters for all measurement methods.
Finally, the risk might be unacceptable for the building at a distance of 50 meters from the slope toe because probability has not reached 0% and expense much money. The risk might be acceptable for the building′s minimum distance of 150meters. Further, the measured dip angles were converted to the projected dip angle based on the plane′s strike. Therefore, based on the engineering design concept, if the design is performed using the C.G.S. data, the engineering design must be very conservative compared to the design using the LiDAR data | en_US |