Mechanical properties of cemented tailings backfill under true triaxial loading condition

The filling mining method can not only achieve the goaf, but also reduce the discharge of surface waste. The backfill is in a complex triaxial stress state in the goaf. If the backfill is damaged, mine production safety will be seriously affected. A true triaxial testing machine was used to load the cubic cemented tailings backfill (CTB) specimens with the size of 150 mm × 150 mm × 150 mm. The failure characteristics, strength characteristics, and strain characteristics of the CTB with different cement-sand ratios of 1:4, 1:6, and 1:8 were studied. The octahedral strength equation of CTB is established under triaxial compression. With the increase of tailings content in CTB, the internal friction angle φ of CTB decreases gradually. The maximum principal strain ε 1 is the main cause of the deformation of the CTB, and the reverse bending point of the volume strain ε v of the CTB is between 0.90 and 0.95 σ c . The theoretical calculation formula of CTB octahedral strength and shear stress theory under triaxial compression is established. The research results are beneficial to better understand the mechanical and deformation behavior of CTB under triaxial loading, and can provide reference for the three-dimensional stress state design of mine filling.