Creep properties and resistivity-ultrasonic-AE responses of cemented gangue backfill column under high-stress area

To investigate the creep and instability properties of a cemented gangue backfill column under a highstress area, the uniaxial compression creep tests were conducted by single-step and multi-step loading of prismatic samples made of cemented gangue backfill material(CGBM) under the high stressstrength ratio. The creep damage was monitored using an electrical resistivity device, ultrasonic testing device, and acoustic emission(AE) instrument. The results showed that the CGBM sample has a creep hardening property. The creep failure strength(CFS) is slightly larger than the uniaxial compressive strength(UCS), ranging in ratio from 108.9% to 116.5%. The instantaneous strain, creep strain, and creep rate increase with increasing stress-strength ratio in the single-step loading creep tests. The instantaneous strain and creep strain decrease first and then increase during the multi-step loading creep process. The axial creep strain of the CGBM column can be expressed by the viscoelastic-plastic creep model. Creep instability is caused by the accumulation of strain energy under multi-step loading and the continuous lateral expansion at the unconstrained middle position during the creep process. The creep stability of a CGBM column in a high-stress area can be monitored based on the variation of electrical resistivity, ultrasonic pulse velocity(UPV), and AE signals.