The problem of selecting the most effective device for creating concentrating stresses on the borehole contour when using non-explosive destructive mixtures (NDM), allowing to create a main crack between contour boreholes in a row and to save the roof of the chamber from groundwater breakthrough into the excavated space, is considered. Laboratory studies carried out on samples of gypsum powder monolith and natural gypsum blocks of an underground mine confirmed the theoretical data on the effectiveness of using twin metal inserts for directional fracturing of gypsum rocks using NDM.
