Technical and economic basis for determining the boundary of transition from open-pit to underground works Technical and economical elements in the determination the boundary of open pit and underground mining

Abstract

In determination the limit of open pit and underground mining technical and economical factors are to be considered. The ratio of overburden and waste rock stripped to the ore reserve is the principal criterion of utility of the open pit mining. Many attempts were made to give the mathematic solution of this problem, but complicated formulas and mistakes in mathematic interpretation prevented from using it in practice (see Part 3). The purpose of this article is to give the solution of this problem on the base of determination of the most profitable open pit. It is possible to give the general formulas (9) and (10) showing the expenses concerning the mining of the deposit by two variants: a part of deposit (A) is mined by open pit and another part (C) by underground method (Fig. 2); all tonnage of deposit (A + C) is mined by underground method. In the part 8 of this paper a few examples of this method are illustrated.

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