Late mechanical properties and energy evolution mechanism of cemented tailings backfill under early damage

Cemented tailings backfill (CTB) is a composite material prepared using cement, tailings and water. During early mining operation, CTB is inevitably subject to failure and damage caused by human or equipment crushing. However, the current literature is silent on the condition of the CTB after early damage. In this study, an analysis method of mechanical properties and failure models of early damaged CTB based on energy evolution was proposed which provided new ideas to reduce the failure and collapse analysis of CTB in mines. The results show that the early damage had significant effects on the late mechanical properties, energy evolution, failure model and microstructure of the CTB. Moderate early damage improved the later loading capacity of CTB. The UCS increased and then decreased in the late CTB at damage ages 3 d and 7 d, whereas it continued to decrease at ages of 14 d and 21 d. The early damage input energy was divided into releasable elastic deformation energy dominated by compression intensive deformation and plastic deformation energy dominated by damage deformation. The total energy after maintenance of the damaged CTB was the sum of the undamaged CTB energy and the early elastic deformation energy and then removed the plastic deformation energy. The late CTB failure model was from shear damage to tensile damage and then to mixed tensile-shear damage, which showed a certain damage effect. Combined with the economic benefits and the late mechanical properties of the damaged CTB, the CTB with a damage age of 7 d was more advantageous.