Integrated slope stability analysis of metasedimentary rocks in the Tarkwaian formation in Ghana using kinematic and limit equilibrium methods

Abstract Slope stability assessment in metasedimentary mining environments presents unique challenges due to complex discontinuity networks resulting from both depositional and metamorphic processes. This study employs an integration of detailed discontinuity characterization, kinematic analysis, and multiple limit equilibrium methods to evaluate slope stability in two adjacent open pit walls (P1 and P2) within the Tarkwaian Formation, Ghana. Systematic window mapping across 240 m of pit walls combined with laboratory testing, established site-specific geotechnical parameters. Kinematic analysis indicated pronounced stability differences: P1 exhibited critical planar failure risks (90.91–100% of poles in failure zones for the major joint sets), high toppling potential (up to 100% in P1T4J2), and multiple wedge failure intersections. In contrast, P2 showed substantially lower risks across all failure mechanisms. Limit equilibrium analysis using Bishop, Janbu, Spencer, and GLE methods quantified these differences under varying hydrogeological conditions. P1 produced factors of safety (FoS) of 1.156–1.170 (unsaturated conditions) and 0.898–0.904 (saturated), indicating potential instability under saturation. P2 maintained higher stability, with FoS values of 1.292–1.299 (unsaturated) and 1.089–1.091 (saturated). Sensitivity analysis identified the friction angle as the most influential parameter affecting the stability of the slopes, followed by unit weight and cohesion. P1’s stability showed 40% greater sensitivity to parameter variations than P2 which reflects the impact of unfavourable discontinuity orientations on rock mass stability.