Conditions of changing of extra-hard rock into weak rock under the influence of tectonic stresses of massifs

Experimental investigations of the last two decades have Bade it possible to confirm the presence of the tectonic component of rock stresses or the tectonic component of rock proseare. Tectonic stresses have saem determined by in situ measurements in underground working! and test wells present in mines (6Q£ of igneous deposits and 20% of sedimentary ones mainly) which are situated on the territory of Europe, Asia, America and Australia. In a number of regions the values of tectonic stresses are 10-20 fold the level of possible gravitational stresses (Markov 1977).