Mechanical response and acoustic emission characteristics of cement paste backfill and rock combination

Abstract Backfill mining method plays an important role in the treatment of tailings, and the failure law of a cement paste backfill (CPB) and rock combination under pressure has essential guiding significance for the safe production of mines using the backfill mining method. In this work, uniaxial compression acoustic emission (AE) experiments were conducted on single CPB and CPB–rock combinations with different cement tailings ratios, based on referring to fractal theory to investigate the crack evolution of the specimens at different stages. The results show that the content of the tailings has a significant influence on the crack evolution and AE characteristics at the different stages of the CPB. When the cement tailings ratio of the CPB is reduced from 1:4 to 1:10, the crack evolution in the compaction stage gradually changes from initial crack closure to tailing–cement cracking. The crack evolution in the instability stage changes from the production of a large number of microcracks to that of several macrocracks. After entering the instability stage, the elastic energy release of the upper rock in the combinational specimens aggravates the post–peak damage of the CPB, and the change in the fractal dimension changes from “rising with severe fluctuations” to “declining with small fluctuations”. There are significant similarities in the ring–down count fluctuation laws of the rock and CPB in the combinational specimens. Before approaching the stress peak, the ring–down counts and fractal dimensions of the specimens show a significant downward trend. Among them, the fractal dimensions of the CPB–rock combinations with ratios of 1:4, 1:8, and 1:10 decrease by 21.1%, 16.7%, and 16.8%, respectively. The research results of this work can provide guidance for predicting the instability and failure of a CPB–rock combination in a mine using the backfill mining method.