Evaluation of the effects of three different cooling methods on the dynamic mechanical properties of thermal-treated sandstone

A systematic understanding of the physical and mechanical behavior of high-temperature rocks after different cooling methods can provide a theoretical basis for underground coal gasification and geothermal resource exploitation. In this study, a series of tests were carried out, including wave velocity and split Hopkinson pressure bar (SHPB) test, to analyze the dynamic mechanical properties of thermal-treated sandstone with different heating temperatures (25 degrees C, 200 degrees C, 400 degrees C, 600 degrees C, 800 degrees C) under nature, water, and liquid nitrogen cooling treatment. The dynamic stress-strain curves of rock were obtained, and the relationships between three parameters (dynamic strength, elastic modulus, and peak strain) and temperature were investigated. The fragments after impact compression were collected for the screening test, and the degree of fragmentation of sandstone after different heating temperatures and cooling treatments was discussed. The results demonstrate that under the three cooling treatments, the wave velocity, elastic modulus, and dynamic peak strength of sandstone decrease with the increase in thermal treatment temperature while the peak strain and fracture degree increase as the temperature rises. When the temperature is higher than 400 degrees C, the physical and mechanical properties of sandstone significantly deteriorate. Compared with natural cooling, the rapid cooling of water and liquid nitrogen more severely damages the thermal treatment sandstone. Moreover, the invasion of water weakens the connection between mineral particles, leading to the most significant deterioration of the mechanical properties.

Automated summary

This study investigated the physical and mechanical behavior of high-temperature rocks after different cooling methods. The results showed that increasing temperature led to deterioration in the dynamic mechanical properties of the rocks, while rapid cooling methods caused more severe damage.