The Characteristics of Coal Rock Brittleness at Low Temperatures

In specific domains, rocks are subjected to extremely low temperatures, where the phenomenon of brittleness significantly impacts the stability of rock engineering applications. This research seeks to investigate the brittleness of rocks at low temperatures by exposing coal rock samples with varying moisture contents to temperatures ranging from -175 to 25 °C. The brittleness index, derived from mechanical testing, was employed to characterize the brittle behavior of coal rocks within the specified temperature range. The findings indicate that the brittleness of coal rocks is affected by different degrees of water saturation. Specifically, in coal samples with varying moisture levels, brittleness initially increases and then decreases as the temperature decreases. Notably, coal samples with medium water saturation exhibit the most pronounced increase in brittleness. To further clarify this evolutionary process, nuclear magnetic resonance (NMR) analyses were conducted on coal rock samples with differing moisture contents, both prior to and following a freezing process. The results suggest that frost cracking and the behavior of pore ice jointly influence the evolution of brittleness in these materials.