Extraction of ore reserves from undermined protective pillar under open pit bottom

Abstract

One of the problems in ore mining is untimely preparation of ore reserves for extraction. Eventually, mining efficiency drops. Aiming to replenish quickly depleting reserves, mining of various-purpose pillars is undertaken. For this reason, studies into safe mining of pillars are relevant and essential. For instance, for a gold mine in ground conditions of pronounced geological and structural uncertainty, for the sustained short- and-medium-term production, a method was validated and proposed for extraction of ore reserves from the undermined crown pillar left under the open pit bottom. In the framework of this research, a geomechanical model of an ore deposit has been developed in the form of a conceptual flow chart of mining of a crown pillar under an open pit bottom at the preserved production infrastructure condition by surface and underground mining. 3D numerical modeling uses the finite element method. The calculations find that underground mining of the undermined protective pillar under the open pit bottom, due to considerable jointing of the steeply dipping ore body, is limited by expansion of wide possible rock damaged zones up to the ground surface.

Failure Mechanism and Stability Control Technology of Slope during Open-Pit Combing Underground Extraction: A Case Study from Shanxi Province of China

“…For horizontal or near-horizontal coal mines with miscellaneous coal seams, it is economically unreasonable to open-pit mine the deeper resources, and a combination of open-pit mining method and underground extraction method is generally used [4][5][6][7]. This form of mining is also known as the method of open-pit combing underground extraction (OPUG) [8][9][10][11][12]. In the process of OPUG, the effects of underground and opencast mining are both mutual superimposition, forming a large dynamic composite system, so the deformation mechanisms of slopes and rock bodies are more complicated, and the slope already formed within the opencast mine will be affected by the disturbance of the underground mining.…”