Integrated Geotechnical Assessment of Deep Open-Pit Slope Stability Under Structural and Hydrogeological Conditions

Abstract

The following abbreviations are used: acoustic borehole televiewer (ABI40), uniaxial compressive strength (UCS), factor of safety (FoS), two-dimensional finite-element program RS2, and three-dimensional finite-element program RS3. The stability of deep open-pit slopes is governed by structural heterogeneity, rock-strength variability, and hydrogeological conditions. This study develops a multi-level geotechnical-domain framework and assesses the design slopes at the Vasilkovskoye gold deposit by cross-validating structural-kinematic, limit-equilibrium, and numerical methods. The database comprises two oriented geotechnical boreholes, GA-01 and GA-02, drilled to 753 and 713 m, ABI40 data, and laboratory testing, including 61 uniaxial compression, 30 triaxial, and 50 Brazilian tensile tests. Dips, RocPlane, SWedge, Slide, RS2, and RS3 were applied at bench, inter-ramp, and overall-slope scales. UCS ranges from 4.11 to 247.27 MPa in quartz diorite and from 1.11 to 278.76 MPa in granodiorite. Deteriorating drainage reduced FoS from 2.80 to 1.75 (37.5%) in quartz/mixed diorite and from 2.64 to 1.63 (38.3%) in granodiorite. For the Sector 2 planar mechanism, RocPlane and RS2 yielded FoS values of 1.60 and 1.80. For unweathered rock, sector-specific bench face angles of 70–80° and inter-ramp slope angles of 53.8–60.0° were justified, whereas weathered zones require flatter geometry. In engineering practice, these values are screening-level, site-specific parameters rather than transferable design angles: implementation requires sector-specific kinematic checks, drainage verification, piezometric control, and deformation monitoring. The framework provides a scale-dependent basis for prioritizing structural control at bench scale, domain strength and geometry at inter-ramp scale, and groundwater management at overall-slope scale.