Abstract
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 °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 °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.
Highlights
Temperature is one factor that can alter the physical properties in rock
Note that each sample type, characterized by grain size and the room temperature strength assessment, is consecutively numbered from 1 to 10; these numbers are provided in the first column of Table 2
Residual strain may increase in heated sandstones of high uniaxial compressive strength, very low uniaxial compressive strength (< 20.0 MPa), and low uniaxial compressive strength (20.0–40.0 MPa), with the exception of 100 °C. These laboratory tests aimed to determine the influence of temperature on the value of residual strength and residual strain of Carboniferous sandstones in the Upper Silesian Coal Basin (USCB), employing temperatures from room temperature to 1000–1200 °C
Summary
Temperature is one factor that can alter the physical properties in rock. As temperature increases, thermal expansion of rockforming minerals weakens the rock mass and may cause its destruction (Dimitriyev et al 1969; Heuze 1983; Somerton 1992; Den’gina et al 1994; Hajpál and Török 2004; Sygała et al 2013; Cieślik 2015). Many institutions around the world have researched the physical, mechanical, and thermal properties of rocks under high temperatures (Hettema et al 1993; Yavuz et al 2010; Brotóns et al 2013; Lu et al 2016; Tian et al 2016). Results from this past work clearly show that rock quality changes with temperature (e.g., Tian et al 2012, 2014; Shi and Jinyu 2015). Datasets are wide-ranging, and it is difficult to characterize uniformly the behavior of rocks under high
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