Abstract.

The application of the Disturbance Factor (D) in the stability of rock slopes has been the subject of much debate among practitioners since its first appearance in the paper Hoek et al. (2002). For mined slopes, it is generally accepted that rock masses are subject to near-field or shallow disturbance due to the effects of blasting and/or mechanical excavation, and deeper disturbance due to unloading. One of the sources of debate is related to the distribution of disturbance within the rock mass. In limit-equilibrium analyses techniques, the disturbance is often modeled using a series of one or more discrete disturbance layers or zones, within which D is held constant. There are a number of approaches that can be used to define the boundaries between these layers, including: empirical techniques, blast damage modeling, numerical analysis, and experience based engineering judgment. However, all of these methods generate artificial boundaries between the disturbance layers which are often exploited by the search routines used to identify the least stable failure paths. This paper proposes to represent D as a function of ó3 in the Hoek-Brown formulae, thereby modeling disturbance as a continuum rather than discrete layers. This method allows the use of any function of ó3 that represents a variation of D and can then be used to generate principal-normal or shear-normal stress functions, which can be input directly into commercial stability analysis software. Examples of the application of this method are presented in this paper.

1. Introduction

The application of the Disturbance Factor (D) in the stability of rock slopes has been the subject of much debate among practitioners since its first appearance in the Hoek- Brown Failure Criterion in 2002 [1]. For mined slopes, it is generally accepted that rock masses are subject to near-field or shallow disturbance due to the effects of blasting and/or mechanical excavation, and deeper disturbance due to unloading. One of the sources of debate is related to the distribution of disturbance within the rock mass. In limit-equilibrium analyses techniques, the disturbance is often modeled using a series of one or more discrete disturbance layers or zones, within which D is held constant.

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