A new technique has been developed for the determination of ultimate strength in uniaxial extension by testing results of samples of arbitrary shape. This technique consists in the sample failure with spherical indentors and measuring of sizes of rupture surfaces and zones of failured rocks at contacts with indentors for the subsequent estimation of ultimate stress state. The revised formulas were obtained for calculation of ultimate strength in uniaxial extension with using the method of sample failure with spherical indentors, essentially improving the accuracy of the technique.
The Article considers the rheological tests of rock samples being carried out with using the direct (classical) and quick-acting (stepwise) techniques. In the stepwise test of one sample a family of creeping curves was obtained. The comparable tests have shown a satisfactory similarity of test results obtained in various testing techniques.
Complex investigations have been conducted of rheological properties of undisturbed and disturbed rocks under laboratory conditions in the modes of creeping, relaxation and lateral pressure. It was stated that the rheological properties of disturbed rocks substantially differ from those properties of undisturbed rocks. Recommendations are given for the use of the obtained results in solution of tasks in mining geomechanics.
The method has been developed for the determination of indices of strength certificate of rocks using the technique of specimen’s failure with oncoming spherical indentors. This method is based on the assessment of ultimate stresses acting in the tensile plane and within the zones of failured rocks under action of indentors at the moment of sample splitting. Formulas were obtained for calculation of indices of strength certificate, i.e. cohesion and angles of internal friction under tensile compression and nonuniform triaxial compression, ultimate strength in uniaxial compression and tension. This method is applicable in situ conditions.
