Characterizations of macroscopic deformation and particle crushing of crushed gangue particle material under cyclic loading: In solid backfilling coal mining

In solid backfilling coal mining (SBCM), the deformation resistance of crushed gangue particle material (CGPM) is critical for controlling overburden strata movement and ground surface subsidence. In engineering practice, CGPM is generally circularly compacted first by the compaction machine to reduce its compressibility. However, a systematic approach to guide the compaction practices does not appear to be available. This study implemented an experimental approach to investigate the macroscopic deformation and particle crushing characteristics of CGPM during constant amplitude cyclic loading (CACL) and continuously loading again after CACL (CL-CACL). At the same time, the influence mechanism of particle crushing on macroscopic deformation of CGPM was also revealed. The results show that the residual compression ratio increased with the cyclic loading times in CACL experiments, but in CL-CACL experiments, the final compression ratio decreased with the cyclic loading times that the samples have borne before, which indicates that cyclic loading can significantly improve the deformation resistance of CGPM. It is also shown that the crushing ratio (B_g) increased with the cyclic loading times in CACL experiments. However, it was opposite in CL-CACL experiments. There existed a piecewise linear relationship between the residual compression ratio and the crushing ratio, which indicates the particle crushing is a key factor to leads macroscopic deformation of CGPM. The research can reveal the influence mechanism of particle crushing on macroscopic deformation of CGPM and provide a systematic approach to guide the compaction engineering practices in SBCM.