Technical and technological solutions regarding the development of pillars during final mining of deep open pits

Abstract

When mining operations achieve the total depth of open pits within their boundaries, a significant share of balance ore reserves remains in pillars under transport communications as well as under reloading points. Liquidation of the available transport communications should follow by the development of the new ones. Hence, mining stages of a steep-grade field and periodicity of a pillar initiation within both working open pit flank and temporarily nonworking one have been studied. Нannivskyi open pit has been taken as an example to substantiate the expediency to extract balance reserves occurring under crushing and reloading point within ±0 m level. The substantiation of technical and technological solutions concerning the development of a protective pillar involved cuts of geological ore formation which supported the idea of availability of the preserved reserves and topicality of the selected problem. Operation schedules to mine the pillars have been developed for general conditions; the required equipment set has been analyzed. New technological solutions have been obtained using current excavating and transportation machinery. Engineering solutions as for possibility to open the pillars and liquidate them in terms of the limited technical and technological potential have been substantiated. The technological schemes of pillar mining have been systematized depending upon the technological processes, taking place in the open pit, and the applied equipment set. Scientific significance of the paper is the developed systematization of facilities in terms of operation schedules of pillar mining. Practical significance is the developed operation schedules to mine and liquidate the pillars. Technical and technological expediency to use skip hoist while reactivating temporarily nonworking open-pit walls for rock mass transportation from the pillars up to the surface has been substantiated. It has been proved that during final mining operations in an open pit, complicated by difficulties in electricity delivering to the preservation pillar, it is expedient to apply loaders in one operation schedule. Use of loaders and skip hoist to mine the preservation pillar is the optimum strategy. It has been substantiated that the proposed procedure is more advantageous to compare with the conveyor transport.