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Applicability of Strain Softening Models to Slope Stability Analyses
M. Díaz & R. Ledezma
CODELCO, División Chuquicamata, Chile
The main scope of the current work is to study the use of advanced constitutive models considering strain softening behaviour, such as Itasca´s CaveHoek model, within the context of slope stability analyses. The CaveHoek model was developed specifically by Itasca Consulting Group to describe the rock mass behaviour under caving operations. This paper contributes to the understanding of a unified constitutive model that can be applied in underground mining as well as in open pit mining. In this work, different two-dimensional numerical models were constructed for a slope comparing the model response between CaveHoek model and a more “standard” constitutive model (Modified Hoek-Brown with damage). The results were similar at overall scale for a 500 m-high slope comprised of moderate quality rock mass. In the case of very good quality rock mass, degradation of the strength properties did not develop due to lack of plastic strain. In the case of poor quality rock masses, hardening of the properties may take place if the residual curve is stronger than the peak curve, in particular at very low confinement. In addition, several sensitivity analyses were carried out for key parameters of the CaveHoek model, such as the residual strength envelope.
Finally, a real case application was carried out by studying a representative section of the west wall in Chuquicamata Mine. A good calibration was obtained for the condition observed in June of 2016, showing a marginal equilibrium condition and a failure mechanism in accordance with the field observations. In subsequent work, the modelling was extended to a full 3D representation of the pit, obtaining a reasonable agreement for the current condition reproducing the relative behaviour, in terms of mobilized areas, between different sectors of the west wall.
Velocity contours for June 2016 pit geometry showing unstable sectors in red. Model with SSR=1.1.