Acta Geodynamica et Geomaterialia

Title: INFLUENCE OF GRAIN SIZE, HUMIDITY AND STATE OF STRESS ON THE MECHANICAL PROPERTIES OF SANDSTONES
Author: Bukowska Miroslawa
DOI: 10.13168/AGG.2015.0015
Journal: Acta Geodynamica et Geomaterialia, Vol. 12, No. 2 (178), Prague 2015
Full Text: PDF file (0.5 MB)
Keywords: sandstone, humidity of rocks, mechanical properties, triaxial compression tests
Abstract: Results of conventional triaxial compression tests on medium-grained and fine-grained sandstone samples of the Upper Silesian Coal Basin in Poland, under a full range of strain and two states of humidity, in the air-dry state and capillary saturation state, are presented. The geomechanical properties in the pre-peak and post-peak sections of the stress–strain curve are determined, as well as the equations of the envelope of Mohr's circles, the cohesion, and the internal friction angle. We conducted tests that showed the tendencies of the changes in the stress and strain parameters resulting from confining pressure. The dependence of the critical differential stress, residual differential stress, critical strain, and total strain on the confining pressure were described by linear functions. The dependence of the post-peak failure modulus on the confining pressure for the tested sandstones in an air-dry state was described by a polynomial function. In the tests of sandstones in the capillary saturation state we did not obtain reliable results and further research is required in this area. There are few studies showing the influence of humidity on the pre-peak and post-peak parameters of rocks undergoing conventional triaxial compression tests in a servo controlled testing machine. Our test results have practical applications in forecasting the behavior of rocks located deep underground and in designing safe mining operations.