Theoretical investigations of mechanical properties of sandstone rock specimen at high temperatures

The effect of mechanical load and thermal treatment on sandstone specimen is numerically investigated. Based on Newton’s second law, we established the rate- equation model of sandstone rock specimen under uniaxial mechanic load and fire. We introduce in the model the material nonlinear stress/strain relationship and the effect of material non linearity is analyzed. We show that globally, the amplitude of the internal stress gradually decreases when the temperature increases. The analysis of the internal stress reveals that the combined effect of the thermal treatment and mechanical load on the specimen lead to the rapid damage of the specimen. Heating the specimen to 100°C reduces around 30% of the internal stress. We found that 450°C is a critical temperature of damage for the physical and mechanical properties of this sandstone. Above 450°C of heating, the internal stress tends to fall to zero. Moreover, above this temperature, a significant reduction in strength occurs. This result shows the loss of rigidity of sandstone when the temperature increases and reveals that the fire reduces the mechanical performance of sandstone significantly. The materiel non linearity parameter slowly affects the thermal damage of sandstone.