Influences of water filling timing on the deformation mechanism of crushed gangue in goaf

In order to investigate the effect of different water filling times on the compression deformation of filled gangue, a large-scale crushed gangue deformation testing system was utilized, and two sets of gradient loading experiments were designed. Through rigorous experimental analysis, distinct patterns of deformation during loading and constant load stages are elucidated, with a particular focus on the influence of water filling timing. Quantitative assessment reveals that early water filling induces rapid gangue deformation, primarily during loading stages, while later water filling stages exhibit a heightened impact on constant load stages. Moreover, the study identifies a stepped deformation phenomenon attributed to the irregularities in crushed gangue particles, shedding light on the underlying mechanisms governing gangue behavior under varying water filling conditions. Notably, an in-depth analysis of energy consumption patterns underscores the dominant role of strain, especially in later water filling stages, significantly influencing deformation characteristics. The study further explores the implications of water filling timing on mining subsidence effects, offering quantitative insights into the stability of gangue backfilling. Under the action of the cumulative deformation and concentrated filling effect, the equivalent filling height is slightly higher than that of the early water filling state, but this trend weakens with the increase of mining height. The conclusions of this study can provide experimental data for stability analysis of crushed gangue filling the abandoned mines with different water filling timing.