Constitutive relationship and instability mechanism of acoustic emission damage in cemented fill materials

Cemented paste backfill (CPB) is an effective method for tailings disposal and reducing underground mining accidents. In this study, CPB samples with different cement-to-tailings ratios (C/T) and solidification times were prepared. The mechanical characteristics, acoustic emission (AE) properties, damage equations, crack initiation, and instability precursors of CPB were analyzed through uniaxial compressive strength (UCS), AE, and digital image correlation (DIC) tests considering the C/T and solidification time. The micro-mechanical characteristics of the CPB rupture surfaces were investigated using scanning electron microscopy (SEM). An increase in the C/T or solidification time resulted in more flocculent hydration products, such as calcium silicate hydrate (C-S-H), and a relative decrease in the pores and voids in the CPB. Consequently, the material with a C/T ratio of 1:4 and a curing time of 28 days reached a peak strength of 3.93 MPa. The theoretical damage equation was established by fitting the Weibull distribution parameters to the cumulative AE count damage variable. The modified theoretical damage equation based on the Weibull distribution parameters describes the CPB damage evolution satisfactorily for different C/T and solidification times. The b-value of AE is negatively correlated with the AE damage variable, and the b-value exhibited a sudden decrease near the stress peak. The results of this study can serve as a reference for underground filling mining and for enhancing mining safety.