Load-bearing deformation and strength evolution of a filling body prepared by compacting a gangue waste-slurry mixture

The long-term and high-intensity coal mining has caused a series of serious environmental problems such as surface subsidence, water loss, and gangue stacking. Mixing filling method of gangue and slurry, as one of the most widely used filling methods, can simultaneously achieve strata and surface movement control, water resource protection, and gangue disposal, while the process of filling material forming filling body under surrounding rock pressure and its mechanical properties are unknown. In order to study the mechanical behaviors of the filling body at each load-bearing stage, confined graded creep compaction experiments were conducted on the initial filling body. The solidified filling body formed by creep compaction of initial filling body for different durations was machined to standard specimens to carry out uniaxial compression experiments. Experimental results show that the deformation of initial filling body in the initial stage of creep compaction is dominated by instantaneous deformation, whereas, as the creep compaction duration is increased, it is gradually dominated by creep deformation, and the steady creep rate is slightly influenced by the axial stress. The uniaxial compression tests suggest that the longer the creep compaction duration of initial filling body, the stronger the solidified filling body. That is, the creep compaction of initial filling body is conducive to improving the strength of solidified filling body formed later. Therefore, it is suggested to backfill the goaf in or before the active period of bending and subsidence of overlying strata as far as possible. These results provide a theoretical basis for the mixing filling method of gangue and slurry.