Experimental Study on the Mechanical and Acoustic Characteristics of Cemented Backfill with Unclassified Tailings at Different Curing Ages under Uniaxial Compression

In order to study the influence of the cement–tailing ratio and curing age on the mechanical properties of cemented backfill with unclassified tailings and improve the accuracy of the backfill monitoring method, the mechanical characteristics of the failure process of cemented backfill with unclassified tailings at different curing ages were studied using the acoustic emission and infrasound method. The results show that the peak strength and modulus of elasticity of backfill are positively correlated with the curing age. During the failure process of cemented backfill with unclassified tailings, the acoustic emission ringing count shows a “stabilizing–rising–falling–rising” trend, and the infrasonic ringing count will have a “multiple peak” phenomenon. The ib value of the acoustic emission signal generally increases with the extension of the curing age. The ib value of the infrasonic signal generally has a negative correlation with the increase of the curing age. When the ib value of the acoustic emission and infrasonic wave all start to decline in a jumping manner, this indicates that the backfill is about to be damaged. The dominant frequency ratio of acoustic emission signals (FAE) is distributed between 0–4 during the failure process, and the total number of FAE shows the phenomenon of “first decreasing and then increasing” with the curing age. The dominant frequency ratio of infrasonic signals (Fs) is distributed between 0–6. During the failure process of cemented backfill with unclassified tailings, the quantity ratio of class A and B of acoustic emission signals shows a gradually increasing trend, and the quantity ratio of class A and B of infrasonic signals shows a “decreasing–increasing–decreasing” trend, and the quantity ratio of class A and B of acoustic signals shows a sharp increase at the stage of entering the crack’s unstable growth stage.