Abstract
Subsequent extension of surface subsidence after vertical caving leads to large-scale surface destruction, as well as associated geological hazards. The extension prediction for cylindrical caved space, which appears circular surface subsidence, is still an intractable issue, due to the absence of robust models. To fill such a research gap, this paper provides an analytical model for the depth and orientation where the shear failure of isotropic rocks around the caved space is firstly observed. The anisotropy of surrounding rocks is further involved to enable this model to analyze the slip failure along discontinuities in anisotropic stress state. The prediction for the extension of the surface subsidence in Xiaowanggou iron mine is conducted, and the comparison between the prediction and the observation in satellite images demonstrates the validity of the proposed model. Even though this model cannot provide a definite boundary after extension, the prediction for the orientation surface subsidence extends to contribute to mitigating the effect of geological hazards. Another contribution of this work is to provide guidance to mitigate the impact of surface subsidence on safety and environment, such as filling the interspace between large-sized caved rocks by dumping small-sized waste rocks or backfilling the caved space with waste rocks.
Highlights
The geological hazards due to mining-induced surface subsidence raise public concerns [1, 2]
The analytical prediction for the progressive caving, as well as the associated extension of surface subsidence in these projects, is still an intractable issue, due to the absence of robust model, especially when the rock anisotropy due to discontinuities is taken into consideration. To fill such a research gap, we introduce an analytical model to relate the rock shear failure around the cylindrical caved space, which accounts for extension of surface subsidence, to in situ stress, and the property of surrounding rocks and caved rocks
Surface subsidence due to underground mining leads to severe geological hazards
Summary
The geological hazards due to mining-induced surface subsidence raise public concerns [1, 2]. Despite having been successfully applied in many mining projects, such as Kiruna iron mine in Sweden, El Teniente copper mine in Chile, Río Blanco copper mine in Peru, and Gaths asbestos mine in Zimbabwe, the employment of both Hoek’s and extended models is still restricted because of some basic assumptions: (1) the rock failure and associated surface subsidence occur for a long distance compared with the cross section normal to the strike of ore body, and the analysis can be reduced to a two-dimension problem; (2) the rock mass has homogeneous and isotropic mechanical property, which means the discontinuities (e.g., faults, joints, or beddings) are not taken into account Such assumptions mean Hoek’s and extended models are invalid to analyze progressive caving either around the cylindrical caved space or with the consideration of the rock anisotropy due to discontinuities.
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