Analysis of a Complex Rock Slope Instability with a Stepped Failure Surface using Discrete Fracture Network Models

The failure surface of bedrock landslides is often characterized by a stepped morphology consisting of a combination of pre-existing discontinuities and intact rock bridges. Rock bridges can be represented explicitly using discontinuous planes, or implicitly using apparent cohesion along continuous planes. In both cases, there is a significant uncertainty related to either the persistence of discontinuous planes or the assumed cohesion. In addition, the geometry of the failure surface is often very simplified. Recent developments in modeling software incorporating discrete fracture network model options now allow an explicit representation of both rock bridges and stepped geometry along failure surfaces. Discrete fracture network models also make better use of statistical data concerning discontinuity spacing and persistence. Consequently, they represent a significant progress towards realistic modeling of rock slope instabilities.

This paper presents the analysis of a rock slope instability using a two-dimensional finite element modeling approach incorporating a discrete fracture network model. The study includes both the back analysis of a rockslide, which occurred in November 2012, near Boston Bar, British Columbia, and the assessment of a potential retrogressive failure. The paper describes the parameters and assumptions used to reproduce the stepped morphology of the November 2012 rockslide and calibrate the discrete fracture network model of the potential future instability. The results are compared with a conventional limit equilibrium analysis. This case study is an example of the application of discrete fracture network modeling for the study of complex rock slope instabilities with a stepped failure surface.

Wen, A., Sturzenegger, M. and Stead, D. 2014 “Analysis of a Complex Rock Slope Instability with a Stepped Failure Surface using Discrete Fracture Network Models”, in Proceedings of DFNE 2014, Vancouver, Oct 2014.

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