Alternative fatigue-creep performance of rock-backfill composite structure material in mine stopes under high static stress: Disturbed amplitude effect

This work aims to investigate the dynamic stress amplitude on the mechanical responses of rock-backfill composite structure material under alternative low-cycle fatigue loading and creep loading tests. Results show that deformation, damage propagation, and failure pattern are all impacted by the stress amplitude, and volumetric deformation is the largest for a sample subjected to strong stress disturbance. The equivalent lifetime decreases with the increase of disturbed amplitude. A notable positive interaction between the fatigue damage and time-dependent damage is found, and they promote each other. Additionally, a novel damage evolution model is proposed by the irreversible radial strain, and the model matches well with the testing data. Moreover, post-test computed tomography imaging reveals that cracks at rock-backfill interfaces are relatively easy to be stimulated under low stress disturbance, and it is suggested that tension-splitting failure is more likely to occur within the surrounding rock, and shear failure seems to occur within the cemented tailings backfill for all the tested samples. Alternative LCF-CL tests were performed on RBCS samples.A high disturbed stress amplitude is likely to induce greater volumetric deformation.The cyclic damage and time-dependent damage promote each other.Splitting-tension failure occurs within rock and shear failure is found within CTB.