The tests of the conventional triaxial granite and dolomite compression in the aspect of their mechanical properties

The article presents the results of tests of conventional triaxial compression of granite from the Strzcgom-Sob6tka massif and dolomite from the Zqbkowicc Bqdzifiskic deposit - rocks belonging to two from three basic types determined according to the criterion of their formation. The investigations were carried out using the testing machine with the servomechanism MTS-8 10 and chamber of Karman type in conditions ofcircular pressures up to 70 MPa. The testing machine steering was performed with the longitudinal deformation Velocity of 10-5s-I range measured in the press measuring system by means of piston displacement. The investigations in conditions of conventional triaxial compression (cy, > CF2 C`3 P) were conducted in accordance with ISRM recommendations. Cylindrical samples with diameter of 30 mm and slenderness ratio of 2 were prepared for tests. The tests were carried out at room temperature. It has been pointed out at p = 0 MPa that the samples of dolomites and granites differ regarding the shape of stress-dcformation curves, which particularly in the post-critical area characterise the dynamics of their destruction. The dolomite samples point out in the course of deformation curves features characteristic for the fourth type ofthe destruction curve according to Bukowska (2005b); rarely the destruction runs in accordance with the curve of third type. In case of granite the dominant destruction curve type is the curve of the third type. The following stress and deformation parameters were determined: critical differential stress (boundary strength), residual differential strength, critical deformation determined at maximum stress and residual deformation corresponding with the residual strength. The results of investigations of gcomechanical properties were worked out as functions of circular pressures within the range of 0-70 MPa. Linear functional relationships with high correlation coefficients with respect to tested rocks in the range ofapplied circular pressures up to 70 MPa were presented (Figs. 2-8). A higher increase in the value of tested parameters as a result ofcircular pressure growth for rocks with lower strength at ofp = 0 MPa was pointed out. The parameter the most "susceptible" to circular pressure changes among gcomechanical parameters is the residual strength. The results of the conducted tests were the base for the indicating the cohesion value and the angle of internal friction of both rocks types by the parabolic equation of the envelope of Mohr's circles method.