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The pile-beam composite structure in high-elevation debris flow areas is selected as the research object. Based on characterizing the pile-beam composite structure, the particle-flow simulation analysis program and the explicit dynamic analysis program were used to study comparatively the blocking effects of single-row piles and two-row piles, as well as that of a pile-beam composite structure at different positions. Besides, We simulated the mechanical characteristics of the pile-beam composite structure and discussed debris flow accumulation and structural stress transfer after the blocking. The calculation results show that the blocking effect of the pile-boulder force chain formed by the contact between large-size particles in the debris flow with the blocking structure and side boundaries on both sides of the gully could effectively block and delay the subsequent debris flow movement. The blocking effect of the pile-beam composite structure is the best. Meanwhile, the transition zone between the two-row piles further suppressed the flow velocity. When choosing the position for a pile-beam composite structure, we should consider suppressing the debris flow velocity as early as possible at the beginning and the potential energy-kinetic energy conversion process. Meanwhile, we also need to emphasize the design of the reservoir capacity, beware of the escape of debris flow due to a low-head barrier, and choose the optimal solution for the layout. The impact stress by debris flow boulders will be transmitted to the rear pile through the connecting beams, and the connecting parts at both ends of the beam almost reach the yield strength, which needs reinforcement to strengthen.

The eastern Himalayan syntaxis is one of the regions having the most intense tectonic activities, the most complex geological conditions, and the most frequent geohazards in the world. The planning and construction of engineering projects are faced with four types of catastrophic geo-safety risks, including tectonic faulting in the plate tectonic belt, disaster occurrence of the deep-buried tunnels, instability of loose mountains, and regional geological disaster chain. It is a critical topic in the field of engineering geology how to select relatively stable and safe sites in active tectonic zones to minimize the geo-safety risks of planning, construction, and operation of engineering projects. This paper summarized the major geo-safety problems in the eastern Himalayan syntaxis. Accordingly, it revealed that traditional site selection theories hardly satisfy the requirements of the engineering projects in the eastern Himalayan syntaxis area. The site selection encounters geo-safety challenges caused by unclear geological evolution process and construction, prominent disaster risk of tectonic activity and strong earthquake, weak research on the deep tectonic stress field and disaster evaluation, and severe ultra-high-elevation and ultra-long-runout geological disaster chain. Thus, this paper suggested the main research directions of the site selection from five aspects: (1) regional geological evolution and engineering geological problems, (2) active fault and engineering safety risk, (3) complex in-situ stress field and engineering disaster risk, (4) engineering risk of regional geological disaster chain, and (5) theory and method of site selection in eastern Himalayan syntaxis. This paper provides ideas for improving the risk assessment and prevention methods of site selection of engineering projects.

The dynamic mechanism of high-elevation and long-runout landslides is always a tricky problem in geological disaster research. Due to the complex geological conditions in the Qinghai-Tibet Plateau, high-elevation and long-runout landslides show more complex and robust dynamic action, resulting in disaster chains of ultra-high elevation and ultra-long distance. The article presents a systematic review of the geological characteristics, physical model tests, and numerical analysis of three prominent dynamic effects of high-elevation and long-runout landslides in the Qinghai-Tibet Plateau, namely, dynamic fragmentation, dynamic erosion, and fluidization. Given the current research status of high-elevation and long-runout landslides in the Qinghai-Tibet Plateau, three significant aspects are proposed to be studied in the future: the mechanism of high-elevation and long-runout landslides in extreme geological environments, new methods for model tests based considering size effect, and basin-wide hazard chains induced by high-elevation and long-runout landslides.

Rock‐ice avalanches have frequently occurred in the Eastern Himalayan Syntaxis region due to climate change and active tectonic movements. These events commonly trigger catastrophic geohazard chains, including debris flows, river blockages, and floods. This study focuses on the Zelongnong Basin, analyzing the geomorphic and dynamic characteristics of high‐altitude disasters. The basin exhibits typical vertical zonation, with disaster sources initiating at elevations exceeding 4000 m and runout distances reaching up to 10 km. The disaster chain movement involves complex dynamic effects, including impact disintegration, soil‐rock mixture arching, dynamic erosion, and debris deposition, enhancing understanding of the flow behavior and dynamic characteristics of rock‐ice avalanches. The presence of ice significantly increases mobility due to lubrication and frictional melting. In the disaster event of September 10, 2020, the maximum flow velocity and thickness reached 40 m/s and 43 m, respectively. Furthermore, continuous deformation of the Zelongnong glacier moraine was observed, with maximum cumulative deformations of 44.68 m in the distance direction and 25.96 m in the azimuth direction from March 25, 2022, to August 25, 2022. In the future, the risk of rock‐ice avalanches in the Eastern Himalayan Syntaxis region will remain extremely high, necessitating a focus on early warning and risk mitigation strategies for such basin disasters. [ABSTRACT FROM AUTHOR]

Large-scale three-dimensional (3D) physical modeling is an important method to study landslide-induced impulse waves. In such models, the test randomness is often quite high, which necessitates systematic exploration of the randomness and error. However, only a few relevant studies have been conducted yet. To this end, this study aims to investigate the randomness and error of large-scale 3D landslide-induced impulse wave experiments and provide solutions to the different sources of error. Based on six repeatability experiments with the large-scale 3D physical model of the Wangjiashan landslide-induced impulse wave in the Baihetan reservoir of the Jinsha River, China, the errors of typical physical parameters are classified into systematic errors, which originate from instrumental factors, experimental design, observer bias, environmental factors, and random errors originating from communication and observation. The allowable error rate of landslide motion in the repeatability experiment is found to be 5%, but the dynamic chain transmission of landslide-induced impulse waves leads to the transmission and accumulation of errors, which causes a gradual increase in the errors of landslide motion, primary wave, propagating wave, and run-up process; and the coefficient of variation increases from approximately 3.8% to 25.0%. To reduce the experimental data error, a low-pass filtering model for removing high-frequency noise and a moving window smoothing model for image frame rate mutation are established, which can decrease the coefficient of variation by nearly 1.3%–4.0%. The corrected particle dynamic map exhibits a continuous and smooth flow field, which basically eliminates the velocity field mutation and discontinuity caused by communication data packet loss. Overall, this study can provide theoretical basis and technical support for large-scale 3D landslide-induced impulse wave experiments. [ABSTRACT FROM AUTHOR]