Integrated assessment of open-pit slope stability considering structural anisotropy, strength parameter uncertainty, and slope geometry

Abstract

Purpose. To develop and validate an integrated methodology for open-pit slope stability assessment that provides a traceable transition from structural data of a fractured rock mass to Q′-GSI classification, kinematic analysis, strength parameter calibration, deterministic and probabilistic stability assessment, and quantitative evaluation of the influence of slope geometry. Methods. Structural data from a deposit in the East Kazakhstan Region were processed in Dips using Terzaghi correction for orientation bias and Fisher contour analysis. Q′ and GSI were determined from RQD, Jn, Jr, and Ja. Strength parameters were calibrated in RSData using the Hoek-Brown and Mohr-Coulomb criteria. The simplified Bishop method, the Spencer method, and the General Limit Equilibrium (GLE) method with the Morgenstern-Price interslice force function were applied in Slide2. Findings. Four dominant discontinuity sets were identified from 436 orientations, and values of Q′ = 3.67 and GSI = 55.7 were obtained. The proportion of kinematically feasible elements was 14.83-29.73% for planar sliding and 54.80% for flexural toppling. Four of the six intersection lines between the mean discontinuity sets satisfied the conditions for wedge sliding. For the 51.8 m high profile with an overall slope angle of 44°, the mean FS ranged from 0.9896 to 0.9947, while the probability of failure Pf ranged from 53.6 to 57.8%. The strongest relationship with FS was established for the internal friction angle (r = 0.9863). At a slope angle of 40°, increasing the height from 40 to 60 m increased Pf from 23.5 to 47.9%, whereas at H = 20 m, increasing the slope angle from 45 to 50° increased Pf from 23.9 to 90.0%. Originality. A unified assessment sequence is proposed that integrates structural-statistical data processing, Q′-GSI classification, kinematic analysis, local calibration using the Hoek-Brown and Mohr-Coulomb criteria, probabilistic limit equilib-rium analysis, and assessment of the influence of slope geometry. It is shown that kinematic susceptibility to structurally controlled failure mechanisms and Pf characterize different levels of risk and therefore require joint interpretation. Practical implications. The proposed methodology enables the identification of unfavourable spatial orientations and geometric scenarios, determination of the parameters requiring priority refinement, and simultaneous assessment of stability changes in terms of the factor of safety FS and probability of failure Pf.