The extraction of shallow ore deposits using underground mining methods rather than open pit mining is not uncommon nowadays, especially with the increased environmental constraints. Such scenario results in the creation of a surface crown pillar - the rock cover consisting of ore rocks that separate the uppermost stopes from the overlying surface. Although the problem of surface crown pillar stability has been researched for more than 30 years, the design guidelines are still limited. This is largely because of the wide variety and complexity of site-specific conditions. Thus, empirical and analytical methods are only used for preliminary design and more comprehensive methods such as numerical modelling must be adopted for the final design. This paper investigates strategies for the design of a surface crown pillar at a gold mining operation having a shallow, steeply dipping orebody that extends underneath an existing tailings storage facility. The orebody is in the vicinity of two regional faults. In this study, numerical modelling approaches are developed using the finite difference code FLAC3D 7.0. Critical factors such as in-situ stress regime, major geological structures, mining sequences, slanted surface topography and surcharge are considered. A model parametric study is carried out to investigate the effect of fault properties and horizontal stress ratios on surface crown pillar stability. Mining-induced surface subsidence is then analyzed to shed light on the anticipated maximum differential settlement and distortion developed in the tailings dam foundation as a result of the mining activities. Predicted differential settlement results could serve as another criterion for crown pillar sizing from the perspective of overlying infrastructure stability. The reactivation of two nearby faults due to mining activities is also explored. It appears that larger shear displacements occur on the fault that is parallel to the orebody strike compared to the cross fault.

如今，采用地下开采而不是露天开采的方法来开采浅矿床已经很普遍，尤其是在环境约束日益严峻的情况下。这种情况导致形成了一个表冠冠柱-由矿石岩石组成的岩石覆盖层，这些岩石将最上面的矿床与上覆的表面分开。尽管已经研究了表面冠柱稳定性的问题超过30年，但设计准则仍然受到限制。这在很大程度上是由于特定地点条件的多样性和复杂性。因此，经验和分析方法仅用于初步设计，而最终设计则必须采用更全面的方法，例如数值建模。本文研究了在金矿开采中设计表层冠状柱的策略，该方案具有浅，陡倾的矿体，该矿体在现有尾矿存储设施的下方延伸。矿体在两个区域断层附近。在这项研究中，使用有限差分代码FLAC3D 7.0开发了数值建模方法。关键因素包括原地应力状态，主要地质结构，开采顺序，倾斜的地貌和附加费。进行了模型参数研究，以研究断层特性和水平应力比对表冠柱稳定性的影响。然后对采矿引起的地面沉降进行分析，以揭示采矿活动导致的尾矿坝基础中预期的最大差异沉降和变形。从基础设施稳定性的角度来看，预测的差异沉降结果可以作为确定顶柱尺寸的另一个标准。还研究了由于采矿活动而使附近的两个断层重新活化。与交叉断层相比，在平行于矿体走向的断层上出现了更大的剪切位移。