Behaviors of anthracite under differential cyclic loading (DCL) after wet and dry cycling: Deformability and hysteresis characteristics

Coal, as a key material in underground reservoirs of coal mines, poses safety challenges to the stability of coal-formed dams due to periodic excavation and fluctuations in groundwater levels. This work focuses on the behaviours of anthracite under differential cyclic loading (DCL), also examining the impact of wet and dry cycles on behaviour of coal in coal mine based underground water reservoirs (CMUWR). Seven sets of coal samples and processed coal flakes were subjected to wet and dry treatments. Mechanical tests were conducted using two DCL paths (rapid loading and slow unloading and vice versa). The parameters of poisson's ratio, damping ratio, strain growth rate and phase shift are analyzed. Compared with fast loading, slow loading demonstrated higher damping ratio, strain growth rate, hysteresis ratio, and hysteresis time probability distributions. Moreover, the number of cracks and crack widths observed after wet and dry cycling of the flakes were directly proportional to the number of wet and dry cycles undergone. By understanding the mechanical properties of coal under wet and dry cyclic loading, engineers and researchers can make informed decisions to enhance the stability and safety of underground water reservoirs.