With the primary aim of minimizing the subjectivity induced by the human-coding of the interaction matrix (IM) in the framework of the rock engineering systems (RES) approach, this paper describes a newly developed methodology for coding of the IM in a fully coupled manner. In this way, the subjectivity of the expert (human) coding of interactions is replaced by a systematic and objective methodology based on case histories from an extensive and worldwide database of open-pit rock slope stability (or instability) observations. In addition, a newly developed Mine Slope Instability Index (MSII) has been proposed to evaluate open-pit (in)stability and to assess the potential for open-pit wall collapses. This paper presents a further validation of the MSII methodology using new real cases, that were not employed during first presentation of the methodology, and that help to better support the field applicability of the proposed MSII methodology.

1 Introduction

The ultimate slopes of an open pit mine are generally excavated to the steepest possible angle, as the economic consequences of the excavation angle are significant; for instance, for large scale open pits, changes in slope angle by approximately 2–3 degrees can be measured in hundreds of millions of dollars in project value (Lilly 2002). Steeper slope angles, however, result in an increased risk of slope failure, with consequences that could affect mining operations. Consequently, continual evaluation of the stability of excavated slopes is a vital component of open pit design and operation. Many failure mechanisms in large scale rock slopes are complex and, for instance, they are often a combination of failure along pre-existing geological weakness planes and failure of intact rock (Sjöberg 1999, Franz 2009) which disables the conventional methods to correctly analyse the possible failures. One powerful approach to tackle this problem is the Rock Engineering Systems (RES) paradigm, which was first introduced by Hudson (1992) to deal with complex rock engineering problems from a holistic point of view. The RES approach has been widely used in rock mechanics analyses, such as slope stability (e.g. Zare Naghadehi et al. 2011, KhaloKakaie & Zare Naghadehi 2012a, 2012b), stability of tunnels and other underground excavations, and rock blasting. (See Zare Naghadehi et al. (2011) for an in-depth review of RES applications in other fields such as environmental studies, road construction, marine sediments analysis, etc.).

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