Purpose. The research purpose is to substantiate a rational technology for mining steep-dipping ore bodies based on a complex of geomechanical studies in combined mining of deposits. Methods. Analysis of existing constructive methods for calculating the optimal mining system parameters when mining under-open-pit ore reserves in the zone of influence of surface mining operations, taking into account the natural stress-strain state of the rock mass. Numerical modeling is used to study the geomechanical processes occurring in the mass during the mining of under-open-pit reserves of steep-dipping ore bodies in order to substantiate the mining system with ore shrinkage. The geotechnical mapping of mine workings is conducted directly in the face to determine the mass rating. Findings. The calculation of the optimal parameters for the stope chamber, inter-chamber and inter-level pillars based on a complex of geomechanical studies has shown that the more intense horizontal stresses act in the bottom of the blocks and in the inter-block pillars, in which a large number of board gates have been driven. Originality. For the first time, using high-precision programs and given the nonuniform distribution of horizontal and vertical stresses acting in the mass for the Abyz Mine conditions, it has been revealed that when mining an individual block, the maximum horizontal stresses around the mined-out space reach 10-15 MPa; when mining a group of blocks – 20-25 MPa. Practical implications. The research results can be used in planning and mining with shrinkage of steep-dipping ore bodies during mining of under-open-pit reserves.