Identification of temperature effect on post-critical geomechanical properties of loaded sandstones

Geomechanical changes in the post-critical residual strength and strain of Carboniferous sandstones from the Upper Silesian Coal Basin, Poland, were measured from uniaxial compression tests. Rock samples were subjected to high temperatures of up to 1200 degrees C. Sandstone samples of different grain sizes were collected from all currently exploited lithostratigraphic members of coal-bearing Carboniferous sandstones across the Upper Silesian Coal Basin, including the Upper Silesian Sandstone Series (Ruda Beds and Saddle Beds). The samples were heated to temperatures between 100 and 1200 degrees C, cooled to room temperature, and subsequently tested by uniaxial compression in a servo-controlled testing machine MTS-810 NEW. The analysis of results followed a grain size and room temperature uniaxial compressive strength classification scheme. Normalized indices of the thermal influence on residual strength and residual strain were calculated. The new measure, namely the indices of thermal influence, can be used to predict the stability of rock masses subjected to high temperatures. The conducted research in terms of evaluation of post-critical parameters subjected to high temperatures as well as the method of analyzing the results are novel and are of primary importance from the engineering (mining and geoengineering) applications point of view.