Dynamic characteristics of sandstone after heating at different temperatures in the coal fire area: an experimental study

Abstract

To reveal the law of dynamic mechanical behavior and the characteristics of sandstone in a coal fire combustion area, taking the sandstone in the Rujigou coal fire area of Ningxia as the research object, we used a split Hopkinson pressure bar test device to perform several impact tests. Six temperature grades of 25, 200, 400, 600, 800, and 1 000 ℃ and three impact pressure grades of 0.58, 0.60, and 0.62 MPa were selected as test parameters. The dynamic mechanical parameters and dynamic failure modes of sandstone specimens were studied after heating at different high temperatures under different impact pressures. The results showed that under the same impact pressure, the strain rate of sandstone increased, and the peak stress decreased with increasing temperature. When the sandstone was at the same heat treatment temperature, the strain rate of the sandstone increased with increasing impact pressure. When the impact pressure was 0.6 MPa, the failure cracks of sandstone specimens at room temperature and the heat treatment temperatures of 200, 400, and 600 ℃ appeared on the side surface. The impact ends of the sandstone specimens with heat treatment temperatures of 800 and 1 000 ℃ were crushed. Thermal damage to sandstone in the coal fire area at different temperatures could change its dynamic mechanical properties.