Thermal effect of load platen stiffness during high-temperature rock-mechanical tests

Abstract The accuracy of rock property measurements in real-time heating loading tests has been considered as questionable due to the thermal effect on loading platens. In this study, the impact of steel platen performance at high temperatures (up to 1000 °C) on granite property measurements is analysed by numerical simulations. Simulation results show that a smaller stiffness of the loading platen can result in specific stress redistributions, increasing micro cracks, and peak axial stress reduction of the sample during uniaxial compression. This can subsequently lead to an underestimation of failure stress and strain. However, the decreasing platen stiffness with rising temperature does not produce any remarkable impact on the temperature-dependent property measurements of the selected Eibenstock granite (EG) heated up to 1000 °C. This is related to the progressively decreased strength of EG and the consequently negligible deformation of the softened platen at elevated temperatures. Therefore, the loading platen can still be treated as ideal stiff. Considering the big variations in strengths and thermal response of different rock types, the suggested procedure to obtain reliable rock properties at high temperatures (e.g. above 800 °C) is to perform an evaluation by replicating the lab tests via numerical simulations.