Effects of Temperature and Water on Mechanical Properties, Energy Dissipation, and Microstructure of Argillaceous Sandstone under Static and Dynamic Loads

Abstract

RMT-150B rock mechanics and split Hopkinson pressure bar (SHPB) devices were adopted to investigate the physical and mechanical properties, energy dissipation, and failure modes of argillaceous sandstone after different high temperatures under air-dried and saturation states. In addition, SEM and EDS tests were conducted to investigate its microstructure characteristics. Results showed that both the P-wave velocity and density of argillaceous sandstone specimen decreased with the increase of high temperature, while its porosity increased. Compared with static stress-strain curves, there was no obvious compaction stage for dynamic stress-strain curves, and the decrease rate of dynamic curves after peak strain was obviously slow compared with static curves. Both the static and dynamic strengths of argillaceous sandstone specimens decreased with increasing temperature, and the critical temperature point for the strength of argillaceous sandstone was 400°C. At the same temperature, the specific energy absorption under air-dried state was generally smaller compared with that under saturated state. Both the strain rate and temperature showed significant effect on the failure mode. After 100∼1000°C heat treatment, the granular crystals of the clastic structure gradually became larger, and both the number and average size of the original pores decreased, resulting in the deterioration of mechanical properties of argillaceous sandstone specimen.

Investigation on Damage Characteristic and Constitutive Model of Deep Sandstone under Coupled High Temperature and Impact Loads

“…When temperature increases from 25°C to 900°C, the P-wave velocity decreases from 3982 m/s to 2646 m/s, with a larger decrease of 33.56%, while its porosity increases by 182% after 900°C treatment compared with that at 25°C. This phenomenon is attributed to the thermal expansion of mineral particles and water vaporization of deep sandstone after hightemperature treatment, which is treated as thermal damage [25,26]. Particularly, Jin et al [27] investigated the inner structure and composition change of sandstone after different high-temperature treatments and found that when the temperature was higher than 500°C, the propagation of the original cracks at the boundary of different mineral particles increases and more new cracks are formed significantly due to the internal thermal stress caused by the nonuniform expansion of mineral particles.…”