The methodical aspects of strength, deformation and energy characteristic determination of salt rocks under direct tensile loading of rock specimens in laboratory conditions

Mineral deposit development is impossible without suitable data about mineral and parting properties. Underground facilities and construction stability depend on how rocks can resist increased loads appearing due-to overburden load redistribution during mineral development. Tensile stresses usually cause stability losses. One of the main information sources for mining design is a laboratory investigation of rock specimens behavior under various loadings. The work aims to create the approaches of strength, deformation and energy determination of salt rocks under direct tensile load in laboratory conditions. The studies are carried in the salt rocks of the Verchnekamskoe potash and magnesium deposit. The main direct tensile problems of rock specimens have been analyzed at laboratory conditions. The comparative direct tensile result analysis of salt rocks has been performed depending on the specimen geometry. Based on the laboratory and numerical experiments, the specimen geometry has been suggested considering the stress state mode arising under loading process, grain size, bracing influence. A material has been suggested to enable a good specimen bracing in caps. It has good adhesion both with a salt specimen and with steel surface of a cup. The center device is developed to provide a good coaxial specimen bracing in cups. Also the device is developed to write the axial specimen deformation directly at test section by the three console type transducers set by the scheme of the equilateral triangle; and increases the reliability of the experiment. The obtained results determine the mechanical salt rock characteristics of the Verchnekamskoe potash and magnesium deposit under direct tensile loading.