Purpose - The purpose of this paper is to propose a new combined finite-discrete element method (FDEM) to analyze the mechanical properties, failure behavior and slope stability of soil rock mixtures (SRM), in which the rocks within the SRM model have shape randomness, size randomness and spatial distribution randomness. Design/methodology/approach - Based on the modeling method of heterogeneous rocks, the SRM numerical model can be built and by adjusting the boundary between soil and rock, an SRM numerical model with any rock content can be obtained. The reliability and robustness of the new modeling method can be verified by uniaxial compression simulation. In addition, this paper investigates the effects of rock topology, rock content, slope height and slope inclination on the stability of SRM slopes. Findings - Investigations of the influences of rock content, slope height and slope inclination of SRM slopes showed that the slope height had little effect on the failure mode. The influences of rock content and slope inclination on the slope failure mode were significant. With increasing rock content and slope dip angle, SRM slopes gradually transitioned from a single shear failure mode to a multi-shear fracture failure mode, and shear fractures showed irregular and bifurcated characteristics in which the cut-off values of rock content and slope inclination were 20% and 80 degrees, respectively. Originality/value - This paper proposed a new modeling method for SRMs based on FDEM, with rocks having random shapes, sizes and spatial distributions.

Landslides induced by reservoir inundation are common in Southwest China, negatively influencing hydropower stations. The Wunonglong hydropower station dam was constructed in the upper reaches of the Lancang River, accordingly causing the water level at the Lajinshengu slope to increase by 30 m. A tension crack with a visible depth of 8 m was observed in the upper sector of the Lajinshengu slope after reservoir impoundment for 170 d. In the following days, numerous cracks appeared on the surface of the slope, and the maximum displacement of the slope reached 3.22 m. Then, a large-scale active deformation body within the Lajinshengu slope formed with an area of 2.62 x 105 m2 and a volume of 1.65 x 107 m3. Detailed field investigations, on-site monitoring, and centrifugal model tests were carried out to analyze the surface features, deformation characteristics, and failure mechanism of the Lajinshengu slope. The results show that the slope is an ancient landslide, divided into two parts (i.e. zone A and zone B) by the gully. Zone B is a traction landslide caused by the displacement of zone A. The longterm inundation weakens the soft rock at the slope foot, intensifying the toppling of bedrock and consequently triggering the sliding of the overburden in zone A. The failure mode of the Lajinshengu slope is a typical case of toppling-sliding failure, and the underlying rock toppling drives the overlying sliding. In addition, early identification methods for toppling deformation covered by overburdened soil were proposed based on monitoring data and deformation signs. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).