Sidewall rockburst characteristics of highly stressed circular tunnel under impact load

Abstract

This study investigated the sidewall rockburst characteristics of highly stressed circular tunnel subjected to impact loads resulting from rock blasting or other mining-related dynamic disturbances, aiming at exploring the influence of vertical prestress and dynamic load on sidewall rockburst. Using a biaxial Hopkinson pressure bar (BHPB) system, we studied the sidewall rockburst of a circular tunnel by applying various prestresses (horizontal and vertical static stresses) to a sand prefabricated circular hole specimen, followed by impact loads. The real-time process and strain field of the sidewall rockburst around the specimen were tracked by the high-speed camera and digital image correlation (DIC). The tests reveal that the sidewall rockburst process can be summarized as: calm stage, slab buckling and spalling stage, rock slabs ejection stage, and V-shaped notch formation stage. Furthermore, the sidewall rockbursts exhibit typical dynamic tensile failure. The mechanism of sidewall rockburst under the coupled static-impact loads was summarized, i.e. the static prestress determines the initial stress and strain distribution, and the vertical prestress influences the affected range and strain values of the strain concentration zone; the impact load disrupts the original static stress equilibrium, inducing alterations in the stress and strain of the surrounding rock and triggering sidewall rockburst.

Keywords

• Rockburst
• Spalling
• Vertical prestress
• Circular tunnel
• Impact load
• Biaxial Hopkinson pressure bar