Purpose. The solution to one of the important problems of the underground mining method is to substantiate cost-effective, technologically feasible and safe variants for mining steeply dipping low-thickness ore bodies. Methods. Mining systems are substantiated on the basis of a detailed analysis of the developed and existing experiential variants for mining steeply dipping ore bodies, identifying production and economic disadvantages, as well as their causes. Findings.As a result of the research, the pillar raise performance in the mining system with ore shrinkage has been substantiated. The main parameters of the proposed variants for mining systems with ore shrinkage, intended for expansion-type supports and borehole breaking, have been substantiated. A design has been developed of fastening the material-running raises (MRR) and ventilating raises (VR) on the working and ventilation horizons to ensure their performance in the mining system with ore shrinkage. Originality. For the first time, dependences of dilution and labour productivity on the ore body thickness and the type of ore breaking for blast-hole stoping and borehole breaking for a single and “twinned block” have been obtained. In addition, a certain dependence of the loading and delivery performance on the average fractional composition, as well as on the delivery distance, has been obtained. Practical implications. The research is characterized by scientific innovations created for the first time, which are able to ensure the efficiency and safety of mining operations, while creating the ability to manage the loss of minerals and dilution in the block, as well as reaching their calculated optimal ratio in order to achieve the most cost-effective production rate.

It is advisable to conduct mining operations in the conditions of the ultimate state of the opened massif with an increase in the pit wall slope angles below the limit of effective use of combined motor-conveyor transport in the cleaning-up zone of deep and ultradeep open pit mines to the final depth. Such a design of the pit walls is achieved when mining benches from top to bottom within the boundaries of steep-slope layers with the use of in-bench loaders in the cleaning-up zone. The conditions for the occurrence of irreversible shear deformations in rock layers and the position of the potential sliding surface with an increase in the pit walls slope angle of steeply inclined layers in the conditions of the ultra-deep Kachar iron ore open pit mine to critical values are established. It is advisable to use skips as the load-carrying body of the in-bench loader, the design of the supports of which allows it to be built with a lifting height of more than 30 m with the possibility of moving along the pit wall with variable berm elevations. The main provisions on the selection and justification of the expediency of using a loading device for operation in the deep zone are formulated based on the differentiation of the application zones of cyclic (motor transport) and cyclic and continuous method (combined motor-conveyor transport). In particular, the total costs of transporting rock mass according to the new scheme of combined in-pit transport with the use of a loading device for operation in the deep zone should be less than the costs of transportation according to existing or traditional schemes.

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