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Typhoons are recurring meteorological phenomena in the southeastern coastal area of China, frequently triggering debris flows and other forms of slope failures that result in significant economic damage and loss of life in densely populated and economically active regions. Accurate prediction of typhoon-triggered debris flows and identification of high-risk zones are imperative for effective risk management. Surprisingly, little attention has been devoted to the construction of physical vulnerability curves in typhoon-affected areas, as a basis for risk assessment. To address this deficiency, this paper presents a quantitative method for developing physical vulnerability curves for buildings by modeling debris flow intensity and building damage characteristics. In this study, we selected the Wangzhuangwu watershed, in Zhejiang Province of China, which was impacted by a debris flow induced by Typhoon Lekima on August 10, 2019. We conducted detailed field surveys after interpreting remote sensing imagery to analyze the geological features and the mechanism of the debris flow and constructed a comprehensive database of building damage characteristics. To model the 2019 debris flow initiation, entrainment, and deposition processes, we applied the Soil Conservation Service-Curve Number (SCS-CN) approach and a two-dimensional debris flow model (FLO-2D). The reconstructed debris flow depth and extent were validated using observed debris flow data. We generated physical vulnerability curves for different types of building structures, taking into account both the degree of building damage and the modeled debris flow intensity, including flow depth and impact pressure. Based on calibrated rheological parameters, we modeled the potential intensity of future debris flows while considering various recurrence frequencies of triggering rainfall events. Subsequently, we calculated the vulnerability index and economic risk associated with buildings for different frequencies of debris flow events, employing diverse vulnerability functions that factored in uncertainty in both intensity indicators and building structures. We observed that the vulnerability function utilizing impact pressure as the intensity indicator tends to be more conservative than the one employing flow depth as a parameter. This comprehensive approach efficiently generated physical vulnerability curves and a debris flow risk map, providing valuable insights for effective disaster prevention in areas prone to debris flows. [ABSTRACT FROM AUTHOR]

Qinghai-Tibet Plateau is one of the most seismically active aeras of China and rock mass structures or geological structure are also complex here. Earthquake-induced geological disasters are occurred frequently in this region. Among them, plane failure is often generated on bedding rock slope especially in destructive area of the Wenchuan earthquake which caused numerous casualties and serious economic loss. To reveal failure mechanism of bedding rock slope, this paper studied the seismic response and investigated progressive failure characteristics of the bedding rock slope through a large-scale shaking table test. A bedding rock slope of 45° contained an unfilled joint set with spacing of 0.1 m that dipped at an angle of 34° out of the surface, was conducted in a rigid model box, with a length of 3.47 m, width of 0.68 m, and height of 1.2 m, respectively. A series of tests results show that acceleration amplification factor in horizontal direction (AAF-X) increases with the increase of the slope elevation and acceleration amplification factor in vertical direction (AAF-Z) amplifies at lower part of the slope. When the shaking intensities are over 0.2 g, the slope crest and its vicinity start to show nonlinear dynamic response. Existence of bedding planes let the isoline morphology of AAF-X redistribute and dominate the seismic amplification at the crest. The progressive failure progress of the model under earthquake can be divided into four stages. This novel experiment offers some important insights to mechanism of bedding plane landslides triggered by earthquakes, evaluation stability of slopes under earthquake, and disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

This research aims to explore detailed spatial distribution characteristics, identify key factors weight, and establish an accurate susceptibility regionalization model of coseismic landslides by the Mw 6.6 Iburi, Japan, earthquake sequence of 6 September 2018. Based on the remote sensing interpretation database, 5,977 individual coseismic landslides were delineated, which occupies an area of about 15.26 km2. The relationship between eight key factors and spatial distribution of coseismic landslides were precisely analyzed by the landslide area density (LAD) and landslide point density (LPD) curves. In order to obtain the weight of eight key factors more accurately, this paper compares the similarities and differences of the two curves in the earthquakes with similar magnitude, which was included the Lushan and Jiuzhaigou earthquake in China. According to the weight of eight key factors, the improved weight of evidence method was used to produce the susceptibility regionalization map of coseismic landslides in the Iburi earthquake. The results show that the improved weight of evidence method has better precision and can provide a scientific coseismic landslides susceptibility regionalization map for disaster prevention and mitigation in the Iburi earthquake. [ABSTRACT FROM AUTHOR]

The Dongla Bridge, Muli County, China, is a key access road between counties in Sichuan Province and the only traffic facility for an important 500-kV electricity substation which provides power to nearby counties. In June 2011, during the bridge construction, an unknown landslide, subsequently named the Dongla Ancient Landslide (DAL), was encountered. Local reactivation of a portion of the DAL, termed the Dongla Reactivated Landslide (DRL), was indicated by evident ground deformation at the Dongla Bridge. In spite of this, transportation of some heavy electrical equipment to the substation was scheduled on 9 May 2013. So, to guarantee the stability and security of the bridge became a primary emergency task. Detailed field investigations of the landslide occurrence, monitoring and emergency mitigation construction were carried out in the period between 2011 and 2014. This resulted in a temporary stabilization of the revived landslide and ensured the timely transportation of the heavy electrical equipment. It is thought that the revival mechanism of the DRL is creep, translational sliding, and was mainly triggered by artificial slope-cutting, but also influenced by precipitation, river erosion, and man-made activities in the form of small-scale mining operations. Following complete failure of the DRL, the probability of landslide-dam and dam breach is proved to be small by risk analyses. This paper can provide an insight into the problems associated with the interaction between the human structures and landslide instabilities. [ABSTRACT FROM AUTHOR]

River blocking caused by landslide dams is a common geological disaster in mountainous regions worldwide, threatening the safety of human lives and infrastructure. However, studies on the formation process of landslide dams and the criteria of river blockage are still at an early stage. This paper built a laboratory-scale experimental apparatus for simulating the formation and evolution process of landslide dams, and then carried out a total of 29 experiments. It analyzed the common evolution stages of river blocking, including landslides, dam formation, and dam breaching in detail. Then, we investigated the influences of the landslide volume, the landslide discharge, and the water flow rate on a criterion and the time length of river blockage. The experimental results suggest that the formation condition of a landslide dam is related to the ratio of the landslide discharge to the water flow rate. Based on this understanding, we proposed a dimensionless River Blockage Criterion (RBC) to judge the formation of landslide dams. The criterion indicates that when RBC > 1.5, a landslide dam may form; otherwise, a landslide dam may not form. Additionally, the time length of river blockage was found to be related to the landslide volume and the water flow rate. Subsequently, we proposed a model for predicting the time length of river blockage and verified it by the 29 experimental results. The Baige River-blocking event, which occurred on the Jinsha River, China, in 2018, was used as a case study to further verify the RBC and the proposed model. The results show that the proposed RBC agreed well with reality, and the percentage difference between the calculated and the actual time length of river blockage was 11%. The findings of this study could contribute to the early warning and emergency response of river-blocking disasters. [ABSTRACT FROM AUTHOR]

Mitigation works are very essential for mitigation of debris-flow hazards in mountainous areas. Usually, it is difficult to assess the effectiveness of existing mitigation works in a catchment. This paper presented a method for quantitative assessment of debris flow mitigation measures by using Kanako system, a user-friendly GUI-equipped debris flow simulator that allows good visualization and easy interpretation. Kanako 2D (Ver. 2.04) was applied to a case study at Caijia Gully, Sichuan Province, China. Mitigation works including check dams, drainage channel, and deposition basin were constructed in the gully in 2001 and 2006. Kanako 2D can simulate debris flow from steep area to alluvial fan. 1D simulation was applied for assessing the effect of the check dams at the lower part of the gully, and 2D simulation was applied for the effect of the drainage channel and deposition basin on the alluvial fan. The simulation results indicate that debris flow will cause great damage to residential area on the alluvial fan if mitigation measures were not implemented in the gully. For old dams which have been filled up with deposits of previous debris flows, the results show that they still have the function for controlling debris flow due to the gradient reduction of the channel bed in front of the dams by the trapped debris flow deposition. After the comprehensive control of debris flow including trapping, drainage, and deposition in the gully, the simulation results indicate that the risk on the alluvial fan can be reduced to an acceptable level. [ABSTRACT FROM AUTHOR]

This study analyzes the mechanism of the landslide event at Hsiaolin Village during Typhoon Morakot in 2009. This landslide event resulted in 400 deaths. The extremely high intensity and accumulative rainfall events may cause large-scale and complex landslide disasters. To study and understand a landslide event, a combination of field investigations and numerical models is used. The landslide area is determined by comparing topographic information from before and after the event. Physiographic parameters are determined from field investigations. These parameters are applied to a numerical model to simulate the landslide process. Due to the high intensity of the rainfall event, 1,675 mm during the 80 h before the landslide event, the water content of soil was rapidly increased causing a landslide to occur. According to the survivors, the total duration of the landslide run out was less than 3 min. Simulation results indicated that the total duration was about 150 s. After the landslide occurrence, the landslide mass separated into two parts by a spur at EL 590 in about 30 to 50 s. One part passed the spur in about 30 to 60 s. One part inundated the Hsiaolin Village and the other deposited at a local river channel and formed a landslide dam. The landslide dam had height between 50 and 60 m and length between 800 and 900 m. The simulation result shows that the proposed model can be used to evaluate the potential areas of landslides induced by extremely high intensity rainfall events. [ABSTRACT FROM AUTHOR]

Using the particle flow code (PFC), this work analyses the kinetic features of a landslide which occurred on May 5, 2018 in Mabian, Leshan City, Sichuan Province, China. The analysis is based on geological field investigations and unmanned aerial vehicle (UAV) images. The micro-strength parameters corresponding to the macroscopic characteristics of landslide rock materials are inverted by the method of the support vector machine (SVM) and PFC coupling. Coupled with digital elevation model (DEM), a PFC3D numerical model of this landslide is constructed, and the slope failure process is simulated. In the kinetic analysis, the landslide velocity, displacement, and energy features are taken into account. The results show that the initial stage of a landslide begins with the acceleration of the overall movement, followed by the debris flow deceleration movement. Its total movement duration is about 32 s, of which the main sliding time is about 16 s. The maximum velocity of the landslide mass is 10.2 m/s, and the maximum displacement is 120 m. The kinetic energy of the landslide dominates in the acceleration stage, and the collision and friction energy dissipation dominate in the deceleration phase. The simulation results are in good agreement with the real landslide characteristics and the video interpretation of the landslide motion process. This work could provide a new way to study related landslides as well as a theoretical reference for the quantitative risk assessment and disaster prevention and mitigation of landslides in the area. [ABSTRACT FROM AUTHOR]

In this work, a two-layer depth-integrated smoothed particle hydrodynamics (SPH) model is applied to investigate the effects of landslide propagation on the impulsive waves generated when entering a water body. In order to deal with the open boundary in practical engineering problems, an absorbing boundary method, based on Riemann invariants which can be applied to arbitrary geometries, is implemented. In order to examine the accuracy of the proposed formulation, the model is tested against both available laboratory tests and numerical examples from the literature. Then, it is adopted to model the characteristics of the impulse waves generated by the Halaowo landslide in the Jinsha River, China. The results provide a technical basis for the emergency plan to the Halaowo landslide and benefit the disaster prevention policy, which helps mitigating future hazards in similar reservoir areas. [ABSTRACT FROM AUTHOR]

A giant soil landslide named Boli landslide occurred on the right bank of Taozi Gully, a branch of the Jiami River in Taozi town, Sichuan Province, China, at approximately 5:40 am local time on 19 July 2018. The landslide destroyed 186 houses and nearly 300 acres of agricultural land in Boli village. Real-time evacuation was successfully implemented to avoid casualties of 281 people among 65 settlements due to the effective warning. This study revealed the typical characteristics, the cause, and the failure mechanism of Boli landslide on the basis of multi-temporal remote sensing images, field investigation, and analysis of the landslide soils. A simple, effective, and scalable community-based early warning system was also proposed in the study on the basis of real-time evacuation in response to landslide hazards in mountain in near future. Moreover, the experience and the effective risk avoidance mode of this study can be used by the concern parties to improve the disaster prevention and countermeasures of poor mountainous areas. [ABSTRACT FROM AUTHOR]