Browsing by Author "Lin, Ming-Lang"

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Effects of seismic anisotropy and geological characteristics on the kinematics of the neighboring Jiufengershan and Hungtsaiping landslides during Chi-Chi earthquake
(2009-03-10)
Dong, Jia-Jyun
;
Lee, Wang-Ru
;
Lin, Ming-Lang
;
Huang, An-Bin
;
Lee, Yen-Liang
The Chi-Chi earthquake (Mw=7.6) of September 21, 1999 triggered many landslides in central Taiwan. Two of these landslides, Hungtsaiping (HTP) and Jiufengershan (JFES) were situated as close as 2 km from each other but had significant differences in their kinematics. JFES landslide was a catastrophic rockslide-avalanche and the HTP landslide was relatively slow-moving. The authors conducted a study to explore the reasons for such differences. Factors such as the characteristics of strong ground motion, sliding direction of landslide, and friction angle of the sliding surface were considered in the study. An analysis of 12 strong-motion records collected in the study area showed that the distribution of horizontal pseudostatic coefficients, earthquake energy ratio and permanent sliding-block displacements (Newmark displacement) were anisotropic with their predominant direction mostly in the E/W-ESE/WNW trending. This direction is perpendicular to the axis of the main geological structures of the studied area. The computed Newmark displacement in the sliding direction of the JFES landslide is larger (44%) than that of the HTP landslide with sliding surface inclination of 21 degrees and friction angle of 28 degrees We can conclude that the seismic anisotropy and the corresponding sliding direction are important contributing factors to the kinematics of studied landslides. The back-calculated friction angle of the sliding surface that corresponds to a critical Newmark displacement for the JFES landslide is about 3.5 degrees higher than that of HTP landslide. The material (colluvium) on the sliding surface in HTP should be less velocity-dependent than that of the JFES landslide (rock) according to the back calculations. The importance of seismic anisotropy, sliding direction, and mechanical properties of sliding surface on the kinematics of deep-seated landslides is demonstrated. (c) 2007 Elsevier B.V. All rights reserved.
Evaluating failure mechanisms of dip slope using a multiscale investigation and discrete element modelling
(2019-12-20)
Weng, Meng-Chia
;
Lin, Ming-Lang
;
Lo, Chia-Ming
;
Lin, Hsi-Hung
;
Lin, Cheng-Han
This study proposed an in-depth multiscale analysis procedure to identify the dip slope area and assess dip slope stability and influencing area. The proposed analysis procedure comprised five stages: (1) identifying the potential area of a dip slope, (2) analyzing the possible failure types of the dip slope, (3) evaluating slope activity, (4) analyzing dip slope stability under the influence of possible triggering factors, and (5) assessment of the deformation and deposition area. To validate the proposed procedure, the Chaochouhu region of Taiwan was analyzed as a dip slope case. In stages (1) to (3), the scale of the utilized map and the precision of associated data were evaluated to identify the potential area of a dip slope, the possible failure types, and the activity of each slope unit. In stages (4) and (5), the processes of deformation and sliding in a high-activity slope unit were simulated using the discrete element method. The numerical model was first verified using in-situ monitoring data obtained from inclinometers. Subsequently, the model was used to predict the slope behavior under conditions of wetting deterioration of geomaterial. The multiscale analysis revealed comprehensive information regarding the dip slope. The application of the proposed approach would be useful to civil engineers for evaluating dip slope stability as well as to relevant authorities for planning hazard mitigation strategies.
Failure mechanism of a mudstone slope embedded with steep anti-dip layered sandstones: case of the 2016 Yanchao catastrophic landslide in Taiwan
(2019-11-01)
Lin, Cheng-Han
;
Hung, Ching
;
Weng, Meng-Chia
;
Lin, Ming-Lang
;
Uzuoka, Ryosuke
On September 28, 2016, the torrential rainfall carried by Typhoon Megi induced a catastrophic mudstone landslide in the Yanchao District of Kaohsiung City, Taiwan. The total volume of the sliding mass was approximately 8700 m(3), which blocked an industrial road and displaced a duplex house in the downslope, leading to three deaths. Unprecedentedly, the 2016 Yanchao land-slide was large and quickly raised public awareness regarding the possibility of large landslides that could occur in the nearby mudstone areas. Based on field surveys, topographic and geological maps, unmanned aerial vehicle (UAV) photography, and remote-sensing imagery, the failure mechanism of the 2016 Yanchao landslide is described in this study. The results revealed that steep anti-dip layered sandstones embedded with the mud-stones play a critical role in large, rainfall-induced landslides. In the case of Yanchao landslide, the bedding joint between two formations was associated with the runoff infiltrating the low permeability mudstone. The kinematic process of the landslide consisted of two phases: a circular failure in the lower formation (alternation of mudstone and sandstone) and the subsequent regressive failure in upper formation (thick sandstone interbedded with mudstone). This study discloses the role of steep anti-dip layered sandstone influencing mudstone slope failure behaviors and presents a preliminary guide for assessing large, rainfall-induced landslides in mudstones. The results could also provide useful information for calibrating the numerical modeling of large landslides that may occur in the mudstone area in the future.
Landscape evolution characteristics of large-scale erosion and landslides at the Putanpunas Stream, Taiwan
(2018-01-01)
Lo, Chia-Ming
;
Weng, Meng-Chia
;
Lin, Ming-Lang
;
Lee, Shun-Min
;
Lee, Kuo-Chen
This study used multi-temporal terrain and remote sensing images to investigate the geomorphological evolution of the Putanpunas stream caused by large-scale erosion and landslides over the last decade. Discrete element method was then performed to gain the physical insight of the slope failure mechanisms and landslide movement. Our results show topographical changes in the alluvial fan downstream and the deposits in the midstream and downstream segments of the Putanpunas Stream between 2005 and 2009. In 2009, torrential rainfall induced large-scale landslides (the volume was about 8.4x 10(7) m(3)) that greatly altered the terrain of the Putanpunas Stream valley and the alluvial fan. A thick, unstable layer of colluvium (the thick of colluvium more than 150 m) was also deposited in the valley. In 2012, further large-scale landslides turned the colluvial layer into debris flows that cut across the Ryukyu Terraces downstream to the downstream segment of the Laonong Stream to the south-west. The change of debris flow direction from southeast to south-west eventually posed a considerable threat to the safety of protected targets and the access road downstream.