Behaviour pattern of rock mass haulage energy intensity in deep pits

A significant portion of mineral deposits developed by open-pit mining is opened to the full depth by road transport ramps without the use of combined transport. In most cases, this is dictated by the high rate of a pit deepening and multi-stage development. In this study, the energy intensity of rock mass (RoM) haulage from the working zone of a pit to the surface is considered at several hierarchical levels. Mineframe software was used to study 3D-models of open pits with different slope angles in order to test the method of analytical calculation of a pit volume that allowed ensuring accuracy under a wide range of mining conditions. The findings of the research are as follows: with an increase in the pit bottom diameter, the zone of stabilization of rock mass lifting (haulage) height shifts to greater target depths. An increase in the pit slope angles entails shifting the weighted average height to deeper elevations. By increasing the pit target depth, combined modes of transport become more economical in comparison with dump trucks due to an increase in the total volume of rock mass. Depending on the comparison purpose, it was proposed to use different types of energy intensity. For a broad estimation of the rationality of the pair “scheme of opening - mode of transport” for open pits, the ratio of potential energy intensities of rock mass haulage of a considered option of a pit opening and its basic option without transport berms was used. The ratio of potential energy intensities as a function of a pit depth was determined. The values of total energy intensity of rock mass haulage from a pit to the surface were also established.