Mechanical response characteristics and damage evolution mechanisms of deep rock masses under coupled loading–unloading-support-disturbance effects

Abstract

To reveal the mechanical response characteristics of deep rock masses under the complete engineering disturbance chain of “stress loading, excavation unloading, support reinforcement, and cyclic disturbance,” this study employed a true triaxial testing system combined with acoustic emission monitoring to conduct rock mass failure tests under coupled loading–unloading-support-disturbance actions. Results indicate that unloading is the dominant factor inducing rock mass damage and degradation, reducing strength by 31.57% compared to static loading. The superimposed disturbance effect further decreases the strength by 17.40%. Support partially restored rock strength and stiffness, increasing them by 7.29% and 10.37%, respectively, compared with pure unloading. Unloading increased dissipated energy per stress increment, and support achieved a dual effect of “energy dissipation and damage suppression” by inhibiting repeated crack reopening. Along the undisturbed path, damage accumulated slowly early and then exhibits a concentrated late-stage jump. Under disturbance, damage followed an “increase during loading, gradual change during unloading, and sharp surge at failure” pattern, with a markedly smaller rise in the damage variable at final instability than under the undisturbed path. Under disturbed conditions, intact rock showed the Kaiser effect, whereas unloaded rock subsequently exhibited the Felicity effect, supporting delayed Felicity onset, enhancing stress memory and disturbance resistance.