真三轴条件下含不同层理倾角硬岩隧道岩爆孕育演化特征OA

To investigate the effect of inclination on rockburst characteristics in deeply buried layered hard rock tunnels,true triaxial rockburst tests were conducted on yellow sandstone specimens with seven inclination angles(0°,15°,30°,45°,60°,75°,and 90°).Acoustic emission(AE)system was used to monitor the rockburst evolution process.Firstly,the macroscopic failure characteristics of specimens with different inclination angles were analyzed,including the failure location,failure mode,and crater features.Secondly,the rockburst evolution process was examined based on AE parameters,including ring-down count,absolute energy,FA-RA characteristics,and b-value.Finally,engineering support suggestions and precursor indicators were proposed.The results show that bedding planes cause a shift in the failure location of the specimens.As the inclination angle increases,the peak rockburst stress,peak AE ring-down count and its occurrence time,and the average maximum depth and width of rockburst craters all follow a U-shaped trend.The peak AE ring-down count is positively correlated with the failure severity,and strong rockburst occurs when the peak value is reached.The specimen with an inclination angle of 60° shows the closest proportions of tensile and shear cracks.The AE b-value fluctuates during the initial loading stage due to the compaction of pre-existing cracks and bedding planes.It increases with increasing stress and drops sharply just before rockburst.Sudden changes in AE ring-down count and b-value can serve as effective precursor indicators for rockburst prediction.