Abstract: Confined loading, creep observations, water immersion, unloading experiments about broken coal gangue which has different water content were performed. The results showed that during the compression process, the stress-compression ratio relation can be fitted as a non-linear curve by exponential function; after the test, the significant particle breakage phenomenon occurred, the non-uniform coefficient increased and the effective particle size decreased and the fragmentation degree of water immersion specimens was greater than that of dry and natural state of waste rock; the axial additional compression occurred to coal gangue after water immersion, the compression rate of this process increased by 9.68%, accounting for 37% of the whole process, “collapsibility” phenomenon occurred; through the analysis, the mechanism of water immersion collapsibility of coal gangue is that, water softening and water lubrication on the coal gangue particles made the particles re-broken and further adjustment of the position, resulting in the coal gangue compact once again.

Key words: coal gangue, compaction, water immersion, collapsibility