Sustainability of the open pit mining and technical system (MTS) is one of its key goals in the changing conditions of the external and internal environment. All MTS’s subsystems must function in concert to achieve this goal. The structure of the MTS is formed by many subsystems and elements, which are evaluated by a significant number of indicators. A comprehensive assessment of the MTS for all possible indicators is a complex and time-consuming task. However, each subsystem and element of the MTS has a different effect on the sustainability of this system. The MTS’s parameters change significantly during transition periods, for example, at a new stage of open-pit mining or when switching to an open-underground method of developing mineral deposits. The MTS’s sustainability declines during the transition periods. Changes in the parameters of technological processes during these periods can have a negative impact on the state of the economic and social subsystems of mining enterprises, as well as on the environment. Ensuring the sustainability of an MTS during transition periods requires the development of new approaches and principles for managing the work of mining enterprises, based on the alignment of economic goals, with goals in the field of ecology and social development. The study substantiates the key role of one of the MTS subsystems—the opening-up of an opencast system (OOS). It is shown that this system has a decisive influence on sustainable functioning and development. The systematization of the principles of sustainable functioning and development of mining enterprises and its systems has been carried out. Four groups of principles are distinguished: system-wide principles of management, principles of development of mining enterprises, principles of MTS development, and principles of the MTS’s subsystem development. The proposed system of principles is based on the idea of a sequential transformation of the subsystems at all stages of design and operation. A feature of the proposal system of principles is the consideration of economic, social, and environmental aspects to ensure the specified parameters for the sustainable functioning and development of mining enterprises. The results of the analysis of the factors of the external and internal environment of the MTS are presented. The parameters and indicators for assessing the sustainability of OOS and MTSs were selected and substantiated. The justified parameters and indicators were ranked using the fuzzy Analytic Hierarchy Process (AHP). The results of the assessment showed a high convergence of expert opinions on a group of economic parameters, which were rather high in technical and technological parameters. However, there is a divergence of expert opinions on social and environmental parameters. As a result of the study, it was concluded that the current management decisions are aimed at ensuring the economic and technological sustainability of MTS functioning, while achieving the goals of sustainable development of this system is not ensured. The methodology developed and presented in the study can be used to assess the sustainability of the functioning and development of MTSs.
