Аңдатпа
Purpose. To establish the relationships governing the influence of the Geological Strength Index (GSI) and the dip angle of a thin ore body on the size of the potential failure zone in the stope roof, and to substantiate an approach for using this zone when selecting technological parameters of stope extraction. Methods. The study was conducted using two-dimensional finite element modelling in RS2 according to a full 4×4 factorial design with GSI values of 35, 45, 55, and 65 and ore-body dip angles of 20, 25, 30, and 35°. The model depth was 400 m, the stope width was 12 m, the stope height was 4 m, and the inter-stope pillar width was 8 m. The potential failure zone was defined as a contiguous near-contour region with a Strength Factor ≤ 1.0. Findings. A consistent reduction in the potential failure zone was established with increasing rock-mass quality. As GSI increased from 35 to 65, the mean z value decreased from 3.48 to 1.71 m, corresponding to a reduction of 50.8%. For individual dip angles, the reduction in failure-zone size ranged from 48.5 to 52.5%. The maximum value, z = 3.65 m, was obtained at GSI = 35 and a dip angle of 20°, whereas the minimum value, z = 1.59 m, was obtained at GSI = 65 and a dip angle of 25°. Within the investigated range of 20-35°, the influence of dip angle was substantially weaker than that of rock-mass quality and exhibited a non-monotonic pattern. Descriptive decomposition of the numerical matrix showed that 97.6% of the total variation in z was associated with differences between GSI levels, 2.3% with changes in dip angle, and approximately 0.1% with the combined and residual component. The mean relative disturbance coefficient Kz decreased from 0.871 at GSI = 35 to 0.429 at GSI = 65. Originality. The dominant role of rock-mass quality in the formation of the potential failure zone in the stope roof during the extraction of thin ore bodies has been quantified. Relationships between GSI, ore-body dip angle, and the size of the potentially unstable near-contour region have been established. Practical implications. The results can be used for the preliminary selection of measures to adjust stope and pillar dimensions, exposed span, and perimeter blasting parameters. Direct prediction of dilution requires site-specific calibration considering the actual thickness and morphology of the ore body and field-monitoring data.