The Influence of Stress Concentration and Unloading on Deep Rock Damage and Rockburst Process: A Numerical Study

In deep rock engineering, the failure of roadways often manifests as left-right symmetry. The influence of stress concentration and unloading on the stability of deep engineering is important. This study uses the FDEM numerical method to calculate the crack propagation, stress field, and damaged zone of deep rock after excavation. The result shows the failure process after excavation and reveals the influence of stress concentration and unloading. Under the same burial depth, the circular roadway has the least failure degree, followed by the straight-walled arched roadway, trapezoidal roadway, and rectangular roadway. During the excavation of roadways at depths below 1000 m, “V”-shaped failure zones appear in roadways with different cross-sectional shapes. After roadway failure occurs, the stress concentration zone shifts from the roadway surface toward the deeper interior. The damaged zone of the roadway develops before the formation of macroscopic cracks, and macroscopic cracks emerge within the damaged zone. The “V”-shaped damaged zone guides the “V”-shaped failure that follows the rockburst event. In deep high-stress roadways, rockburst after unloading mainly occurs in the stress concentration zone, whereas failure in the non-stress-concentration zone may be related to the release of normal strain energy of the surrounding rock.