The influence of constitutive model selection on predicted stresses and yield in deep mine pillars – A case study at the Creighton mine, Sudbury, Canada

Abstract

Based on recent advances in modelling the post-yield behaviour of brittle rock, the authors have developed a calibrated inelastic model of the 7,910 level (2.4 km depth) at the Creighton Mine in Sudbury, Ontario, Canada using data collected from the monitoring of pillar dilatancy. While this calibrated model represents a state-of-the-art continuum approach for capturing the progressive development of yield and stresses in mine pillars, alternative state-of-practice approaches (elastic and perfectly plastic material models, for example) represent potentially acceptable options for practical application. The purpose of this study is to examine the influence of constitutive model choice on stress paths throughout the pillar system at the mining level of interest. The strengths and limitations of various material models are compared and contrasted. Elastic models are shown to adequately represent the larger scale pillar system behaviour from a stress transfer perspective, whereas the state-of-art brittle modelling approach is shown to be ideal for understanding specific pillar-scale stresses and yield.

Estimation of in situ stress from borehole breakout for improved understanding of excavation overbreak in brittle-anisotropic rock

“…Given the 'bowl-like' geometry of the basin (Figure 2), at any point around its perimeter, the stress tensor is defined by local structural features. This has been consistently demonstrated from structural fabric in the country rock surrounding the basin (Cowan et al 1999;Santimano & Riller 2012) and through in situ stress measurements at depth in mining settings (Snelling et al 2012;Trifu & Suorineni 2009;Walton et al 2015b). Proximal to the Victoria project, the most prominent second order stress influencer is the Creighton Fault, which has a strike-slip component of movement.…”

“…The choice of dilation angle was made through experience of the authors. Walton et al (2015b) has shown that from back analysis of pillar yield in Sudbury Granitoid, the dilation angle should be approximately 55% of the mobilised friction angle. Given the fact that during the formation of breakout only a fraction of yielded material remains in place providing confinement, this may suggest that the dilatant component for this application should be less than what is indicated from that work.…”

Deep Mining: A Rock Engineering Challenge

“…In a detailed study of spalling-type rock failures in horizontal and inclined civil engineering and mining excavations situated in hard brittle rock masses, Edelbro (2008) found that a cohesion softening friction hardening material model, CSFH, was the most suited model to describe the fallouts observed. This model captures the lack of influence of confining stress on the initiation of cracking in situ as well as the strong influence of confining stress as cracks develop and the influence of post-yield dilatancy (Martin 1997;Diederichs 2003;Walton et al 2015). The problem encountered with this and other more advanced constitutive models of rock mass behaviour is the determination of realistic model parameters for the post-failure region.…”

Moving towards deep underground mineral resources: Drivers, challenges and potential solutions

“…Currently, deep mining at 1000 m depth is common. Wellbore mining methods have progressively reached an all time depth of >7500 m (Gu and Li, 2003;Wagner, 2013;Walton et al, 2015;Wagner et al, 2016). Challenges associated with deep underground mining are numerous, including: excavation stability, rock-stress risk reduction, mine ventilation, underground productivity, human health impacts, human-machine interaction and smart mining.…”