Substantiation of chamber parameters under combined open-cast and underground mining of graphite ore deposits

The move from open-cast to combined mining method of developing Zavalyevsky deposit of graphite is considered in the paper. The selection of chamber dimension satisfying conditions of long-term stability is one of the questions for scientific substantiation of the move to combined mining method of deposit development. With this purpose physical and mechanical properties of graphite and enclosing rocks are determined. Stress and strain condition of rocks around the chambers using the method of finite elements is studied