Work

Structural rock-slope failure analysis in open-pit mines: an integrated workflow based on field mapping, UAV photogrammetry, and numerical modeling

Year: 2026

Type: article

Abstract: We present an integrated stepwise workflow for rock discontinuity characterization and slope stability analysis in structurally complex, highly fractured metamorphic terrains. It combines close-range photogrammetry, field surveys, rock mass classification, kinematic analysis, Finite Element Modeling (FEM), and InSAR monitoring, and is evaluated at the Riotinto mine in Spain, one of Europe's largest active open-pit mining sites. Although each method was independently successful in characterizing discontinuities and evaluating slope stability, only their integration provides a comprehensive assessment. UAV-photogrammetry-derived point clouds enable faster, more detailed extraction of discontinuities, especially from inaccessible and unstable slopes. However, field surveys are more effective in detecting flexural and direct toppling mechanisms, as photogrammetry often fails to capture discontinuities that dip into the slope or are sub-horizontal. Slope Mass Rating (SMR) provides more representative stability assessments than Rock Mass Rating and Geological Strength Index where slope failures are primarily controlled by discontinuity orientation, such as cleavage, joints and faults, rather than intact rock strength. Shear Strength Reduction FEM indicates continuous shear strain bands in the Eastern Zone, consistent with InSAR-measured subsidence of 28.8 mm/yr, low SMR values ≤14, and field mapping of active planar failures and tension cracks. In the Culm Group Slates, high-angle penetrative Variscan cleavage mostly controls wall-scale planar failures where slope dip exceeds cleavage dip, and bench-scale toppling where cleavage is parallel or dips into the slope face. In contrast, the Acid Volcaniclastic Unit is dominated by meter-scale wedge failures associated with brittle conjugate joint sets, possibly developed during post-Variscan deformation.

Source: Engineering Geology

DOI: 10.1016/j.enggeo.2026.109114