Experimental study on deposition characteristics of landslide-induced river blockages under different water levels

Abstract

[Objective] Landslides are a common type of geological hazard that may induce a series of severe secondary disasters when the sliding mass accumulates and blocks river channels. Previous studies have mainly focused on deposition characteristics of landslides in dry channels, while systematic understanding of deposition behavior under the influence of water remains inadequate. The influence of varying water depths on the deposition process and geometric characteristics of landslide materials still needs to be examined. [Methods] Through laboratory physical model experiments, the deposition characteristics of uniform quartz sand with a particle size of 2.5 mm under slope gradients of 35° and 45° were systematically investigated as it slid into dry river channels(water depth of 0 cm) and channels with different water depths(3 cm, 6 cm, 9 cm, and 12 cm). The landslide volumes were set at 500 cm³, 1 000 cm³, 1 500 cm³, and 2 000 cm³. High-speed photography and three-dimensional point cloud scanning techniques were employed to record the deposition process and morphology. The river channel deposition volume ratio λ was defined to characterize the degree of deposition. [Results] Water depth significantly affected the deposition process and morphology of the landslide materials. Under dry river channel conditions, the deposits exhibited an uneven thickness distribution, with a thicker front and thinner rear. In the presence of water, the deposit thickness became more uniform, and a “double landslide head” phenomenon was observed. The river channel deposition volume ratio λ decreased with increasing water depth. At θ = 35°, λ decreased from 0.36 under dry river channel conditions to 0.19 at H = 12 cm, representing a reduction of 47.2%. At θ = 45°, λ decreased from 0.72 to 0.41, representing a reduction of approximately 43.1%. A multiple regression analysis was conducted to establish a prediction model relating λ to water depth, slope gradient, and landslide volume, with their influence on λ ranked as: slope gradient > landslide volume > water depth. [Conclusion] The presence of water significantly reduces the proportion of landslide materials deposited in river channels by increasing resistance and providing a buffering effect. The value of λ increases with increasing slope gradient, and decreases with increasing landslide volume and water depth. It is recommended that further studies incorporate factors such as the gradation of landslide materials and dynamic changes in the riverbed to explore deposition characteristics under more complex conditions. These findings provide a quantitative basis for risk assessment and mitigation of landslide-induced river blockages.

Keywords

landslide hazard / deposition characteristics / river channel deposition volume ratio / water depth / physical model experiment / influencing factors / geological hazard / risk assessment