Microscopic failure mechanism of fiber reinforced ultra-fine tailings backfill

Fiber-Reinforced Backfill(FRB) has obvious advantages in filling the of goafs. To investigate the microscopic damage mechanism of FRB, a series of tests were conducted on glass fiber reinforced ultra-fine tailings backfill with different cement tailings ratios by using compression machine, scanning electron microscope, nuclear magnetic resonance instrument and acoustic emission monitor to systematically analyze the fracture expansion and damage evolution process of FRB from microscopic level. Studies have shown that: the incorporation of glass fiber can improve the initial structure of the backfill material and reduce the initial defects, among which the improvement effect is most obvious for the specimen with 1:12 cement tailings ratio. There are obvious differences between the damage patterns of CPB and FRB. The damage of CPB is dominated by primary fissures through the specimen, with spalling at local locations, while the damage of FRB is dominated by more small-scale secondary fissures, which is caused by the crack-resisting effect of glass fibers on the backfill material. Due to this reason, the acoustic emission(AE) characteristics of FRB and CPB also show a significant difference: the CPB specimen shows an "AE drop zone" in the ringing count after the yield point(about 85% of the peak stress), while the FRB specimen shows an "AE rise zone" in the ringing count after the yield point. The results of the study can not only provide theoretical guidance for promoting the application of glass fiber reinforced backfills, but also provide acoustic emission criteria for predicting the peak strength of FRB materials. © 2022, Science Press. All right reserved.