Slope stability analysis using deterministic and probabilistic approaches for poorly defined stratigraphies

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ORIGINAL ARTICLE

Slope stability analysis using deterministic and probabilistic approaches for poorly defined stratigraphies Mohsen Ghadrdan . Ashley P. Dyson . Tahereh Shaghaghi . Ali Tolooiyan

Received: 22 July 2020 / Accepted: 21 October 2020  Springer Nature Switzerland AG 2020

Abstract The stability of slopes directly affects human lives, the environment, and the economy. Inaccurate geological profiles within numerical slope stability models can lead to potentially catastrophic consequences when model conditions do not appropriately reflect real-life stratigraphy. In cases where localised deposits are prevalent, probabilistic methods are often necessary to accommodate for unknown or poorly defined stratigraphies. Currently, there are no commercial geotechnical software packages that simulate probabilistic constitutive behaviour of materials within finite element methods for large-scale stratigraphic analysis. Instead, commercially available probabilistic methods such as the random limit equilibrium method are incapable of incorporating non-linear constitutive soil behaviour. For this reason, advanced constitutive models are seldom coupled with probabilistically varying soil layers or spatially variable soil parameters. The objective of this research is the implementation of a simplified method for probabilistic stratigraphic analysis within a commercially

available FE environment, providing a technique to assess the effects of stratigraphic uncertainty on slope stability. The proposed method is presented, highlighting the impact of localised thin layers of soft material as well as their frequency and location on the slope of an operational open-pit mine. The significance of these stratigraphic effects is presented through a case study of Australia’s second-largest open-pit mine, at which the stability of a collapsed coal slope is analysed. To improve the reliability of the finite element method for slope stability assessment, the Monte Carlo approach has been incorporated to consider varying shear strength distributions for models incorporating advanced constitutive behaviour. Thicker probabilistically generated deposits of silty material resulted in increased slope Factors of Safety. Similarly, greater proportions of silty deposits within a predominantly clayey interseam produced larger safety factors than slopes without localised thin silty layers. Stratigraphic analysis indicated that the Factor of Safety was most sensitive to localised silt layers at depths greater than 83 m below ground level.

M. Ghadrdan  A. P. Dyson  T. Shaghaghi Geotechnical and Hydrogeological Engineering Research Group (GHERG), Federation University Australia, Churchill, VIC, Australia

Keywords Coal  Slope stability  Deterministic analysis  Random field analysis  Factor of safety

A. Tolooiyan (&) School of Engineering, College of Sciences and Engineering, University of Tasmania, Hobart, TAS, Australia e-mail: [email protected]

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Geomech. Geophys. Geo-energ. Geo-resour. (2021)7:4

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