Modeling of the geomechanical state of the rock massifs being undermined repeatedly

The geomechanical model is proposed and the technology of numerical simulation is developed. Carried out computer simulation of the geomechanical state of the being undermined repeatedly rock massifs of the 3^rd potash level of the Starobin deposit taking into account its structural and strength features, as well as the technological schemes of the primary mining. The regularities of the stress-strain zones formation in the undermined rock mass containing mined out mine workings and inter-panel pillars were determined. It is shown that the stability of the workings located in the undermined areas significantly depends on the time passed since the primary mining and on the location of the workings in the massif relative to the location of the primary mining operations. It is determined that the most dangerous for repeated mining are the areas of generalized shear, since the processes of rock mass movement and failure are most likely to be active in these areas. In the areas of generalized compression, the processes of compaction of caved rock take place. As a consequence, after a considerable period of time, the state of the rock massif in these areas can be treated as approximating to the natural state, without additional structural failures. In such areas, the effective mechanical characteristics of the rock massifs are practically restored. Therefore, the greatest stability of mine workings will be achieved when they are placed in the area of generalized compression stress state in the zone of caved, compacted rocks of the mined out roadways and faces. 

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