To the method of justification of borders between open and underground works

Introduction. Currently, in the development of mineral deposits, the most widely used are open and underground methods. At the same time, open-pit mining is characterized by an extremely negative impact on the environmental situation, while at enterprises that develop deposits by underground methods, labor productivity is lower and, with some development systems, the extraction of minerals is much worse. The possibility of using open pit and underground works at one field makes it possible to use the advantages of each of the development methods, while reducing the negative factors of one of them at the expense of the other. The aim of the work is to assess the impact of technological solutions involving internal dumping on the establishment of a boundary between open pit and underground operations, taking into account the reduction of the technogenic impact on the environment. Methods for determining the boundaries of the open pit can be divided into 2 groups: the first includes methods for determining the boundaries of the open pit by the minimum total costs or the maximum total profit, the other includes methods using the boundary stripping ratio. In this work, when developing an economic-mathematical model, the methodology proposed by Professor A.I. Arsentiev, where profit is used as a criterion for the transition from open to underground work. As a result of the research, an economic-mathematical model was developed and tested to solve the problem of determining the boundary of the transition from open to underground work, based on obtaining additional profit by reducing environmental costs and taking into account the change in the order of dumping. Dependences have been obtained that reflect the change in the economically justified depth of the open pit on the degree of use of the mined-out space, as well as on the area of external dumps. The analysis of the obtained dependences shows that within the established limits and the given modeling parameters, the use of the worked-out space of the quarry allows to reduce the area of external dumps from 13 ha to 2 ha, while the boundary stripping ratio increases to 5.04, and the depth of the open pit increases from 105 m to 116 m. The results of the study can be used in the design of field development by open pit and combined methods.