Large-scale panel destressing is a rockburst control technique that is used to create a stress shadow in the ore pillar to be mined. The technique aims to reduce the pillar burst proneness by deviating the major induced principal stresses away from the concerned zone of interest. The destress panels, situated in the pillar hanging wall, are choke-blasted with high explosive energy density, and the blast-induced damage in the panel is accompanied by stress dissipation and stiffness reduction due to fragmentation in the panel. These two effects are traditionally modeled holistically with stiffness and stress reduction factors α and β, respectively, applied to the destressed zone. This paper focuses on the interpretation of Phase 3 destress blasting results at Copper Cliff Mine (CCM) where a stress increase (rather than decrease) was detected in the ore pillar crown, while a stress decrease was recorded in the ore pillar sill (as expected). It is hypothesized that high mining-induced stress anisotropy in the pillar crown caused blast-induced fractures to propagate in the orientation of the major principal stress, a condition that would hinder the destressing effect in that orientation. To verify the hypothesis, a series of panel anisotropic rock fragmentation and stress dissipation factors are iteratively tested in a 3-dimensional back analysis of the Phase 3 destress blast. The analysis takes into consideration the stope extraction schedule per the mine plan to better replicate the mining-induced stress condition in the panel and the ore pillar. The results show good agreement with stress measurements taken in situ using borehole stress cells installed in the ore pillar prior to destressing. The paper discusses the implications of preferential fracture propagation orientation and how it might affect the efficiency of destress blasting.

中文翻译：

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应力各向异性对大规模去应力爆破效率的影响

大型面板去应力是一种岩爆控制技术，用于在待开采的矿柱中产生应力阴影。该技术旨在通过将主要诱导主应力偏离相关感兴趣区域来减少支柱爆裂倾向。位于立柱挂墙的去应力板采用高爆炸能量密度进行扼流爆破，爆破对板的破坏伴随着板内碎裂引起的应力耗散和刚度降低。这两种效应传统上是通过分别应用于去应力区的刚度和应力降低因子 α 和 β 来整体建模的。本文重点解释了铜崖矿 (CCM) 第 3 阶段去应力爆破结果的解释，其中在矿柱冠部检测到应力增加（而不是减少），而在矿柱基台中记录到应力减少（正如预期的那样） ）。假设柱顶的高采矿应力各向异性导致爆破裂缝沿主要主应力方向扩展，这种情况会阻碍该方向的去应力效果。为了验证该假设，在第 3 阶段去应力爆炸的 3 维反分析中反复测试了一系列面板各向异性岩石破碎和应力耗散因子。该分析考虑了每个矿山计划的采场开采计划，以更好地复制面板和矿柱中的采矿应力条件。结果表明，在去应力之前，使用安装在矿柱中的钻孔应力单元进行的原位应力测量结果非常吻合。本文讨论了优先裂缝扩展方向的影响以及它如何影响去应力爆破的效率。