Rock Slope Stability Analysis by Using Integrated Approach

Abstract

Slope stability assessment is an essential aspect of mining and civil engineering. In this study, Songwe open-pit mine in Malawi was investigated to establish possible pit slope instability. In performing the analysis, an integrated approach entailing rock mass characterisation, kinematic and numerical methods were applied. Based on rock mass classification system, Songwe Hill carbonatite rock mass is characterised as a good rock but still it possesses numerous random discontinuities that present a complex challenge in geotechnical engineering. Dip 6.0 software was used in carrying out kinematic analysis based on the attributes of discontinuities. The results show that there is a 16% likelihood of planar failure in the divided slope sections of the planned pit. Thus, slope angle optimisation to 41˚ has been proposed as a counter-measure to minimise the potential risk of planar failure. At the optimised angle, the risk of planar failure could be reduced by 44%. On the other hand, wedge failure was found to be improbable since no joint intersections were found in the critical zone of potential failure. For numerical analysis, finite element code was applied using FLAC 3D 5.0 application. The results demonstrate that overall slope angle of 41˚ would offer a favourable balance between safety and mining economics as mining operations progress to deeper horizons thereby avoiding a costly push back solution due to instability.

Geotechnical study for analyzing slope stability between two mining pit boundary

“…Given that the algorithm developed in the numerical method is an approximation algorithm, the term iteration will appear in the algorithm, namely the repetition of the calculation process. In academic research and engineering practice, the numerical approaches of continuum modeling and discontinuous modeling have gained wide popularity (Fish and Belytschko, 2007;Moses et al, 2020). The parameters and variables used in this research are data from the geomechanics laboratory test results, the dimensions of the slope, the shape of the pit, which is adjusted to the final low wall model of the pit belonging to PT-X under study.…”

Evaluation of the Influence of In Situ Stress on the Stability of Mine Pit Walls: A Case Study of Songwe Mine

“…In the first scenario, shear strain behaviour on the pit-slope was investigated at the current planned depth of 250 m. The planned depth is within the bounds of proven ore reserve hence the geological confidence is high. The second scenario is for 280 m depth and the third case is based on the ultimate depth of 300 m. At this depth, the geological confidence is relatively low since less than 10% of the drilled holes reached 300 m. The analysis was performed at the trial steep overall angle of 45º (Moses et al, 2020) in the non-associated flow rule (ψ=0°) and associated flow rule (ψ≠0°). The two flow rules are conducted to comprehend both the worst-case and idealistic scenario of rock mass deformation.…”

Slope design in brecciated carbonatite complexes under high-stress regimes

“…Carbonatites, which are igneous rocks containing more than 50% modal primary carbonates and less than 20 wt. % SiO 2 (Simandl & Paradis 2018;Woolley & Church 2005;Xu et al 2015), are generally competent rock masses with Rock Mass Rating class II rating 60-74 (Moses, et al 2020). However, carbonatite complexes are highly affected by the later stage hydrothermal and carbo-hydrothermal phases where expelled fluids in 2 fissures lead to the formation of new weak features like Mn-Fe veins and/or damage of the rock.…”