Effect of thermal damage on mechanical and permeability properties of sandstone

The objective of this analysis is to investigate the mechanical properties of sandstone at various temperatures and the evolution of permeability characteristics to provide a reference to the execution of projects in unique operating areas. In this paper, through the uniaxial compression test and triaxial permeability test monitored by acoustic emission (AE), sandstone samples treated at different temperatures were tested. The crack development law of heat-damaged rock under load was studied by means of acoustic emission (AE), and the evolution law of rock mechanical properties and permeability was revealed from the aspect of micro-crack damage propagation. The experimental results show that the temperature rises to a certain threshold temperature (200°C in this study), as the treatment temperature increases, physical and mechanical parameters such as P wave velocity, elastic modulus, and peak strength will increase, and the permeability will decrease. After the threshold temperature is exceeded, the physical and mechanical properties of sandstone decrease sharply, and fractures are formed and expanded in large numbers, resulting in a sharp increase in permeability. Affected by the crystal softening of quartz and feldspar and crystalline surface slippage, the rock volume and the number of micro-fractures have increased dramatically, leading to significant changes in the physical and mechanical properties of sandstone in the temperature range of 200°C to 600°C. It was also found that the permeability of all samples at different temperatures exhibited three different stages, namely, a slow decline, a steady rise, and a sharp increase during the entire deformation process. © 2021, Saudi Society for Geosciences.