Research On Rockburst Prediction And Active Prevention And Control Technology For High Geostress Hard Rock Tunnel

Based on the Hongtuzhang tunnel project of Dafenghua Expressway,this paper mainly uses in-situ stress field inversion technology,FLAC^3Dand ANSYS numerical simulation,indoor rockburst test and other research methods,supplemented by PAC multi-channel fully digital acoustic emission detection system and High-speed cameras and other equipment and instruments have carried out research on rockburst prediction and active prevention and control technology for high ground stress hard rock tunnels.The main research contents and conclusions are as follows:（1）Using numerical simulation and mathematical statistics combined in-situ stress field inversion method,the initial in-situ stress field of the mountains along the Hongtuzhang tunnel is explored.The initial ground stress field information of each typical section along the tunnel is obtained.（2）Through ANSYS numerical simulation calculation,the stress of the surrounding rock of the cave wall at different stress release rates was obtained for each section.Based on different rockburst criteria,the rockburst situation along the line was comprehensively predicted,combined with the actual rockburst records on site,Finally,the overall rockburst prediction result of the Hongtuzhang tunnel was obtained.（3）With high-strength concrete materials as the test object,indoor rockburst tests are carried out with the help of monitoring instruments such as acoustic emission instruments and high-speed cameras.First,combining the characteristics of rockburst,an appropriate ratio of concrete with a strength of 80 MPa that can simulate the occurrence of rockburst was obtained through laboratory tests;then,based on this,a relationship between the loading rate and the level of rockburst was established in the laboratory test.Corresponding relationship,and then determined the corresponding loading rate in the test,the indoor test rockburst grade judgment standard using real-time rockburst sound and ejection failure phenomenon,stress-strain curve,and various acoustic emission parameters as the judgment index;Finally,based on this,carry out the experimental research on the anti-rockburst effect of the active and passive bolts,have reached the conclusion that the active support measures,that is,the prestressed anchor are better than the passive support measures in preventing rockburst.（4）Based on numerical simulation methods,by adjusting the key parameters of prestressed bolt spacing,rod length,prestress and other key parameters,a set of supporting parameters of prestressed bolts for different grades of rockburst in Hongtuzhang tunnel was researched and proposed.