Objective Deep coal mining areas in regions such as Inner Mongolia, Shaanxi, Shandong, and Gansu in China feature intricate hydrogeological conditions, which lead to substantial water drainage from roofs and increasingly prominent rock bursts induced by water drainage in overburden confined aquifers. This study investigated the evolutionary patterns of the stress field in coal seams during the water drainage of overburden confined aquifers.

Methods By combining the laboratory charge induction experiments of coals under graded loading with charge monitoring pre- and post-water drainage from a roof in a coal mine, this study systematically examined the variations of induced charge in coals under different stresses, along with the dynamic stress transfer pattern of coals during water drainage from roofs.

Results and Conclusions  Laboratory experiments indicate that the induced charge in coal samples exhibited a nonlinear growth trend with a gradual increase of loaded stress, effectively accounting for the stress applied to coals. Field monitoring results reveal that during the water drainage from the roof, the average charge and its coefficient of variation (CV) decreased within the water-rich zone while the charge first increased and then decreased in a certain range outside the water-rich zone, peaking at a certain position. This finding suggests that the stress was dynamically transferred outwards from the margin of the water-rich zone, with the presence of a transfer range threshold. Based on the times when the charge peaked at various monitoring points outside the water-rich zone, this study determined the stress transfer characteristics under different water drainage quantities. Specifically, the stress underwent slow, fast, and slow transfer stages sequentially. The experiments of pressure relief through large-diameter boreholes verified the effectiveness of the proposed technology in reducing the stress concentration under the water drainage from roofs and preventing rock bursts. The results of this study provide a theoretical basis and technical support for the prediction, prevention, and control of rock bursts in mines with water-rich zones in roofs.