Abstract: To investigate the distribution characteristics of manufactured sand backfill in pillar and room goaf and its influence
on pillar bearing capacity,a goaf backfill treatment project in Hunan Province was taken as the engineering background,
and physical model tests and numerical simulations were combined. The flow and roof-contacting laws of backfill slurry
in goafs under self-weight action were investigated. Then,the enhancement effect of backfill on pillar strength was revealed. The
results show that,when manufactured sand backfill slurry was injected based on self-weight,the angle of repose formed in the
goaf is approximately 14°. After adding fly ash and cement,the fluidity of the backfill slurry is significantly improved,and the
angle of repose is reduced to 10°. After backfilling,when the pillar is loaded,the backfill exerts a restraining effect on the lateral
deformation of the pillar. In this study,when the backfill rate is less than 50%,the restraining effect is relatively weak,and
the external load is almost borne by the pillar;the peak strength of the pillar increases slightly,and the failure mode shows as "
X"-shaped tension-shear cracks. When the backfill rate exceeds 50%,the restraining effect becomes obvious,and the backfill
shares part of the load. The peak strength of the pillar increases significantly,and the post-peak bearing performance is also effectively
improved. When the backfill rate reaches more than 90%,the peak strength and post-peak bearing capacity of the pil
lar are significantly improved. Due to the restraining effect of the backfill on the pillar,the bearing potential is fully exerted.
The cracks have little impact on the bearing capacity of the pillar. The study results have certain theoretical and practical significance
for goaf disaster prevention and control,and provide a reference for further study and engineering practice in related
fields.