Study on the influence of cross-section shape on rockburst of deep tunnels under impact disturbance
The occurrence of rockburst in deep tunnels is closely related to impact disturbances,and the tunnel cross-sectional shape further affects the process and characteristics of rockburst.Based on the world's first biaxial split-Hopkinson pressure bar apparatus,the two-dimensional high-stress tunnel sidewall failure test function under impact loading conditions was developed.Rockburst tests were conducted on specimens with circular hole,D-shaped hole and rectangular hole,all subjected to same coupling of static stress and impact load,to explore the influence of cross-sectional shape on tunnel rockburst.The high-speed camera and DIC were used to unveil the rockburst process and strain field evolution of the specimens.The test results indicate that the rockburst process for specimens with different cross-sectional shapes can be summarized into four stages:the calm stage;crack initiation,propagation,penetration stage;spalling stage and rock fragment ejection stage.There are significant differences in the rockburst characteristics among specimens with different cross-sectional shapes.In circular hole specimens,the strain concentration zone is located at the centerline of the hole,and cracks transition from arc to"V"shape,resulting in the least severe rockburst and a tensile failure mode in the surrounding rock.D-shaped hole specimens have strain concentration zones in the straight wall area between the arch foot and shoulder,with cracks transitioning from arc to"V"shape,primarily demonstrating tensile and tensile-shear failure modes.Rectangular hole specimens experience the most severe rockburst,with a strain concentration zone spanning the entire sidewall,and cracks transitioning from straight line to"V"shape,also primarily demonstrating tensile and tensile-shear failure modes.Rectangular hole specimens show the highest overall deformation rate with a maximum strain value of 0.003 4,followed by D-shaped specimens with a maximum strain value of 0.002 9,and circular hole specimens show relatively lowest deformation rate with a maximum strain value of 0.002 2.Comparative results suggest that circular hole sections can optimize stress or strain distribution,improve the overall structural stability of tunnels,and result in lower severity of rockburst.D-shaped and rectangular hole sections may experience stress concentration due to their irregular shapes,making them relatively more susceptible to damage and resulting in a higher severity of rockburst.
rock mechanicsrockburstdeep tunneltunnel cross-sectional shapeimpact disturbancebiaxial split-Hopkinson pressure bar
万方数据
维普
