1 Introduction

In a paper published in 2013, Yaméogo et al. showed how rock failure could affect stress measurements performed using the so-called modified doorstopper technique developed at Polytechnique Montréal. The modified doorstopper stress measurement technique (Corthésy et al. 2016) often categorized as an overcoring technique, consists in recording the recovered strains caused by stress relief at the bottom of a borehole drilled in a rock mass and converting the relieved strains into stresses by using the deformability parameters at the measuring point. The recovered strains are monitored using a specially designed data logger (Fig. 1) which is linked to a modified doorstopper cell. The recovered strains are converted to stresses assuming the rock behaviour is linear elastic and anisotropic. If rock failure occurs during the measurement process, the stress tensor calculated by assuming an elastic behaviour can be wrong. Core discing is probably the most visible manifestation of core failure when performing such measurements, however, even if no visible signs of damage are present, plastic strains can be induced at or near the borehole bottom, affecting the recovered strains and the calculated stresses (Corthésy & Leite 2008). When Yaméogo et al. (2013) published their work, no interpretation model that could account for the progressive failure occurring prior to or during the stress relief drilling process was available. Recently, Corthésy et al. (2016) proposed using the inverse problem approach for interpreting modified doorstopper stress measurements. In this abstract, the potential for using this approach when progressive failure occurs during the stress measurement operations is evaluated.

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