An investigation of cross-sectional spatial variation with random finite element method slope stability analysis

The selection of two-dimensional cross-sections for plane-strain slope stability analysis often requires a range of assumptions such that the most appropriate cross-section is considered. When faced with complex strata, surface topologies and pore-water pressure distributions, the selection of an appropriate cross-section is non-trivial. Circumstances are further complicated when considering spatially variable soils and heterogeneous strength parameters. In this study, the effects of spatially variable geotechnical parameters are examined for a range of two-dimensional random finite element method (RFEM) simulations of an open-pit mine. A distinct set of random field instances are provided to each cross-section to isolate the impact of geometry and strata variation when coupled with spatially variable soil characterisations. Particular attention is given to the regions providing the greatest impact on factors of safety and representative slip surfaces for each slope geometry, evaluating the need for full three-dimensional RFEM simulation. Further statistical analyses are conducted to establish which random field slope stability cross-sections are significantly different from the underlying cross-section population, thereby identifying the best cross-section to represent the overall slope geometry.