Effects of water loss states on instantaneous and long-term mechanical properties of anthracite during drying process

Water content plays a crucial role in determining both the instantaneous and long-term mechanical behavior of rock materials, a factor that is particularly important in underground mining and excavation projects. This study conducted laboratory tests on bituminous coal under various moisture states during the drying process to investigate both the instantaneous and creep mechanical properties of the coal samples. The experimental results indicate that the uniaxial compressive strength, elastic modulus, and peak strain all increase with the degree of dehydration, and the failure mode transitions from localized failure to through-failure. Additionally, the creep test results show that as the degree of dehydration increases, both the creep strain and steady-state creep rate decrease significantly. By combining the isochronous stress-strain curve method and steady-state creep rate method, the long-term strength of coal samples at different moisture states was calculated. The results reveal that long-term strength is greatly influenced by the dehydration degree, with limited changes observed in the low dehydration stage, while significant enhancement occurs in the high dehydration stage. Based on the laboratory test results, the mechanisms by which moisture state influences the mechanical properties of the samples during the drying process are analyzed.