Excavation-induced stresses have the potential to trigger instabilities around underground openings due to disturbance of the pre-mining stress field. Production sequence is a critical aspect in underground mining as it controls the stress distribution in the rock mass. The cut-and-fill mining method requires consideration of the mining sequence to mitigate the instability risk due to excessive stress concentration in stopes scheduled for production. This study covers the effects of production sequence on the crown pillar and the global mine stability using numerical modeling. A transition from open pit to underground mining in Western Türkiye was investigated. The orebody is a long-narrow vein type steeply dipping metallic mineralization that has three uniformly striking sub-sections. 2D and 3D elastoplastic models were used to examine the crown pillar deformations in alternative production scenarios. Large-scale effects of producing the orebody sub-sections in various orders were studied considering the global mine stability.
Transition from open pit to underground mining is a common practice in metal mining. Although geomechanical restrictions are vital, the economy is also a dominant factor to set the limits of the surface operation. The crown pillar is an essential structure and a portion of the orebody that is left in place to sustain the stability of underground openings. Xu et al. (2019) studied the full recovery of a crown pillar by simultaneously replacing it with an artificial pillar. There are various studies on the determination of crown-pillar thickness using empirical and numerical methods (Chen & Mitri 2021, Dintwe et al. 2022 and Xu et al. 2018). Whittle et al. (2018) established a mathematical method to determine the pillar geometry with no regard for geotechnical stability. Afum et al. (2020) published a similar attempt with a mixed integer linear programming approach. Karian et al. (2016) stated that prevention of stope failure is a crucial aspect of maintaining pillar stability. Some recent studies consider destressing techniques for the reduction of stress concentration on the pillar body (Vennes et al. 2020). Despite the comprehensive research on crown pillar design methodologies, there is no attempt to investigate the production sequence on the crown pillar stability regarding the orebody type and geometry.
