Compaction behavior and residual height ratio of crushed coal gangue under varying support conditions: Experimental analysis and model comparison

Resource utilization of coal gangue and safe recovery of residual coal pillars are the key issues for the green and long-term development of coal mines. The purpose of this study is to explore the compaction characteristics of broken gangue under different supporting conditions and its filling application in goaf. Through the experimental observation and data analysis of the compaction process of broken gangue, the variation law of residual height and residual height ratio under different conditions was studied. The experimental findings demonstrate that the residual height ratio effectively captures the relationship between residual height and the high diameter ratio . In unsupported scenarios, a lower high diameter ratio corresponds to a more favorable stable configuration. Specifically, when this ratio falls below 0.4, the residual height ratio exhibits a substantial increase. Conversely, under supported conditions, the compaction of crushed gangue proceeds in a continuous manner, resulting in enhanced residual height and a notable improvement in the residual height ratio as can to 0.8. The comparative analysis of fitting outcomes reveals that the Terzaghi model exhibits superior aptitude in capturing the compressive deformation characteristics of crushed gangue across varying scenarios, as compared to the Salamon model. This research contribution not only strengthens the theoretical foundation but also offers valuable practical insights for the implementation of coal mine gangue partial filling techniques. • Residual height ratio rises sharply at H/D ratios <0.4; support enhances both residual height and its ratio. • Residual height ratio better links height-to-diameter ratio and stability, especially under support conditions. • PTh model describes gangue creep: rapid initial deformation, logarithmic growth, then stabilization. • Terzaghi model outperforms Salamon in describing crushed gangue compression under confined support.