Landslide hazard assessment generally involves multiple factors and indexes. Based on the theory of extenics with matter-element concept, a method applying the fuzzy extension analytic hierarchy process (EAHP) method is proposed for the comprehensive evaluation of landslide hazard. It can quantitatively show the relative important degree between indexes with the extension interval number. Taking the geological hazards of actual landslide as an example, based upon geological survey and characteristic analysis of landslide field, the author selected 10 influencing factors to analyze the weight of the evaluation index of each level. Through the extension interval judging matrix of evaluation index constructed by the experts, the weight of the indexes was identified and the landslide risk was evaluated step by step with membership function of fuzzy set. The correlation degree of the maximum value was calculated as 0.472, the landslide risk was valued as grade 4, in an unstable state, and at the same time, some feasible measures were put forward to control landslide. The research as described in the paper shows that the fuzzy EAHP method is valid for landslide hazard evaluation.

Under the specific geological conditions of shallow buried coal seams and thin bedrock, the caving method of coal mining can result in irreversible damage to the ecological environment, such as affecting the aquifer structure, causing surface subsidence and creating ground fissures. However, traditional backfill mining faces challenges such as insufficient material, low efficiency and high costs. The paper focuses on the novel ideas of roof cutting and backfilling mining treatment, using Jinjie Mine as the research background. Through theoretical analysis, similarity model experiments and numerical simulation, it investigates the laws of overburden failure, surface movement and deformation under shallow buried and thin bedrock geological conditions when using roof cutting and backfilling mining. The comparative study with the fully mechanized caving mining method shows that the use of roof cutting and backfilling methods can suppress the development of fractures and achieve the effect of reducing subsidence. Before releasing the constraint of the filling gangue column, the maximum direct roof subsidence of the coal seam reached 375 mm, whereas the maximum surface subsidence was 263 mm. After releasing the constraint, the maximum direct roof subsidence of the coal seam reached 541 mm, whereas the maximum surface subsidence was 403 mm. This is significantly smaller than the 2804 mm subsidence observed with the caving mining method. Under the condition of ensuring the filling rate of gangue and lateral constraint, roof cutting and backfilling mining will effectively inhibit the development of a fracture zone and reduce the workload of mine water control. This visual simulation study of the entire backfilling mining process, conducted using similar material model experiments, and the necessary complementary analysis of the actual observed results of the model experiment by numerical simulation, confirms that the roof cutting and backfilling mining method can effectively control surface subsidence and be material self-sufficient.

Utilizing a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach, this study constructs a comprehensive three-dimensional numerical model to simulate particle migration dynamics within rough artificial fractures subjected to the high-energy impact of water inrush. The model explicitly incorporates key governing factors, including intricate fracture wall geometry characterized by the joint roughness coefficient (JRC) and aperture variation, hydraulic pressure gradients representative of inrush events, and polydisperse sand particle sizes. Sophisticated simulations track the complete mobilization, subsequent acceleration, and sustained transport of sand particles driven by the powerful high-pressure flow. The results demonstrate that particle migration trajectories undergo a distinct three-phase kinetic evolution: initial acceleration, intermediate coordination, and final attenuation. This evolution is critically governed by the complex interplay of hydrodynamic shear stress exerted by the fluid flow, frictional resistance at the fracture walls, and dynamic interactions (collisions, contacts) between individual particles. Sensitivity analyses reveal that parameters like fracture roughness exert significant nonlinear control on transport efficiency, with an identified optimal JRC range (14–16) promoting the most effective particle transit. Hydraulic pressure and mean aperture size also exhibit strong, nonlinear regulatory influences. Particle transport manifests through characteristic collective migration patterns, including “overall bulk progression”, processes of “fragmentation followed by reaggregation”, and distinctive “center-stretch-edge-retention” formation. Simultaneously, specific behaviors for individual particles are categorized as navigating the “main shear channel”, experiencing “boundary-disturbance drift”, or becoming trapped as “wall-adhered obstructed” particles. Crucially, a robust multivariate regression model is formulated, integrating these key parameter effects, to quantitatively predict the critical migration time required for 80% of the total particle mass to transit the fracture. This investigation provides fundamental mechanistic insights into the particle–fluid dynamics underpinning hazardous water–sand inrush phenomena, offering valuable theoretical underpinnings for risk assessment and mitigation strategies in deep underground engineering operations.