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The recognition, repetition and prediction of the post-failure motion process of long-runout landslides are key scientific problems in the prevention and mitigation of geological disasters. In this study, a new numerical method involving LPF3D based on a multialgorithm and multiconstitutive model was proposed to simulate long-runout landslides with high precision and efficiency. The following results were obtained: (a) The motion process of landslides showed a steric effect with mobility, including gradual disintegration and spreading. The sliding mass can be divided into three states (dense, dilute and ultradilute) in the motion process, which can be solved by three dynamic regimes (friction, collision, and inertial); (b) Coupling simulation between the solid grain and liquid phases was achieved, focusing on drag force influences; (c) Different algorithms and constitutive models were employed in phase-state simulations. The volume fraction is an important indicator to distinguish different state types and solid‒liquid ratios. The flume experimental results were favorably validated against long-runout landslide case data; and (d) In this method, matched dynamic numerical modeling was developed to better capture the realistic motion process of long-runout landslides, and the advantages of continuum media and discrete media were combined to improve the computational accuracy and efficiency. This new method can reflect the realistic physical and mechanical processes in long-runout landslide motion and provide a suitable method for risk assessment and pre-failure prediction.

With the construction of the Three Gorges Reservoir dam, frequent reservoir landslide events have been recorded. In recent years, multi-row stabilizing piles (MRSPs) have been used to stabilize massive reservoir landslides in China. In this study, two centrifuge model tests were carried out to study the unreinforced and MRSP-reinforced slopes subjected to reservoir water level (RWL) operation, using the Taping landslide as a prototype. The results indicate that the RWL rising can provide lateral support within the submerged zone and then produce the inward seepage force, eventually strengthening the slope stability. However, a rapid RWL drawdown may induce outward seepage forces and a sudden debuttressing effect, consequently reducing the effective soil normal stress and triggering partial pre-failure within the RWL fluctuation zone. Furthermore, partial deformation and subsequent soil structure damage generate excess pore water pressures, ultimately leading to the overall failure of the reservoir landslide. This study also reveals that a rapid increase in the downslope driving force due to RWL drawdown significantly intensifies the lateral earth pressures exerted on the MRSPs. Conversely, the MRSPs possess a considerable reinforcement effect on the reservoir landslide, transforming the overall failure into a partial deformation and failure situated above and in front of the MRSPs. The mechanical transfer behavior observed in the MRSPs demonstrates a progressive alteration in relation to RWL fluctuations. As the RWL rises, the mechanical states among MRSPs exhibit a growing imbalance. The shear force transfer factor (i.e. the ratio of shear forces on pile of the nth row to that of the first row) increases significantly with the RWL drawdown. This indicates that the mechanical states among MRSPs tend toward an enhanced equilibrium. The insights gained from this study contribute to a more comprehensive understanding of the failure mechanisms of reservoir landslides and the mechanical behavior of MRSPs in reservoir banks.

Long-runout rockslides at high altitude have caused lots of severe casualties and huge economic losses in the world, becoming a focus issue in researches on mitigation for large-scale geological disasters. This paper systematically reviews the research process of high-altitude and long-runout rockslides and believes that conventional research on “high velocity and long runout” is difficult to adapt to the requirements of complex geohazards prevention and mitigation in high and extra-high mountains. The methodology on high-altitude and long-runout rockslides has been proposed that includes in the initiation at the high-position, the dynamics of chain-style disasters with a long-runout traveling and the risk assessment and mitigation. Then, the disaster-prone geostructure characteristics and early identification techniques of the high-altitude initiation zone, the long-runout transferring mechanism and boundary layer effect of high-velocity debris avalanche, and risk assessment and mitigation issues have been explored. Through the study in the high mountain and extra-high mountains of the Qinghai-Tibet Plateau indicates that the potential flow transferring mechanism of debris avalanche in high-altitude rockslides, the boundary layer effect of turbulent fluid and the plowing bodies. It is proposed that energy dissipation and risk mitigation methods can be used by modifying the boundary layer bottom slope of high potential debris avalanche, to increase the generation of turbulent kinetic energy in the boundary layer, and the dead zone range in front of barrier piles. Three research directions have been discussed, including the initiating mechanism of disaster-prone geostructure, the dynamic process of high-altitude and long-runout disaster chains, and the theory and technology of risk prevention and mitigation.