Overburden stripping coefficient

OVERBURDEN STRIPPING COEFFICIENT (EN: stripping ratio, barring coefficient; DE: Abraumkennzahl, Abraumkoeffizient; FR: taux de decouverte; ES: coeficiente del desmonte; RU: вскрыши коэффициент) characterizes the quantity of the overburden rocks, which are accounted for the unit of the useful mineral, which has been extracted, or which is subject to the extraction, in case of the opencast method for the development of the deposit. They measure the quantity of the overburden rocks and useful minerals, using the units of the mass and volume (tonne per tonne; cubic metre per cubic metre, cubic metre per tonne).

They distinguish the following major types of the overburden stripping coefficient: the average type is the ratio of the total quantity of the overburden rocks, which are being extracted, within the contours of the open-pit mine or its partial place, to the total quantity of the useful minerals, which are being extracted from the open-pit mine within the same contours; the contour type is the ratio of the quantity of the overburden rocks, which are appended to the open-pit mine in case of the increasing of its depth for one layer (bench), to the quantity of the useful minerals within this layer (bench); the operational type is the ratio of the quantity of the overburden rocks to the quantity of the useful minerals during the certain period of the operation of the open-pit mine or its partial place, this ratio serves as the criterion for the planning of the mining works, and for the calculations of the necessary mining and transport equipment for the period of the operation; the average-operational type is the same overburden stripping coefficient, which is calculated for the entire duration of the operation; the initial type is the ratio of the quantity of the overburden rocks, which have been excavated during the period of the construction of the open-pit mine, to the total quantity of the useful minerals, which are being extracted, within the final contours of the open-pit mine; the horizon-wise type is the ratio of the quantity of the overburden rocks to the quan tity of the useful minerals on the single horizon of the open-pit mine; the layer-wise type is the ratio of the quantity of the overburden rocks within the boundaries of the single layer to the quantity of the useful minerals within the same layer; the planned overburden stripping coefficient (Kp) is determined using the following expression and is used for the repayment of the expenditures, which have been assigned for the overburden stripping works, during the calculation of the "S" production cost of the useful minerals ("Sd" and "Sv" are, respectively, the cost of the extracting works, and the cost of the overburden stripping works); the current type is the ratio of the quantity of the overburden rocks, which are being actually moved into the dumps for the waste rocks during the determined period of the time (month, quarter, the half of the year, the year), to the quantity of the useful minerals, which are being actually extracted during this period, this type characterizes throughout the time the adopted procedure for the advancement of the mining works, and serves as the foundation for the planning of the production cost of the useful minerals; the bounding (limiting, economically expedient, and so on) type is the overburden stripping coefficient ("Kgr"), which is maximally acceptable according to the condition of the economic expedience for the opencast development of the deposit (the major criterion for the identification of the boundaries for the open-pit mines), this type is determined using the following expression

where "Sp" is the expected cost of the useful minerals in case of their extraction using the underground method under the given conditions; "So" is the same cost without the accounting of the expenditures for the overburden stripping works; "Sv" are the expenditures per 1 cubic metre of the overburden stripping works under the given conditions.