| With the rapid development of China’s infrastructure industry,the construction of traffic tunnels is also facing new challenges,buried depth,long tunnels,high stress,hard surrounding rock has been the need to overcome the problem,and in such complex geological conditions,rock explosion has become a major hazard in the construction of unavoidable problems.Therefore,for unexcavated tunnels to carry out advance rock burst prediction and propose a matching support program for the smooth construction of the tunnel is of great significance.In this paper,we use the Dagangshan Tunnel of Lushi Expressway as the supporting project,and invert and predict the full rockburst intensity of the long buried hard rock tunnel by combining ANSYS numerical analysis and multivariate mathematical analysis.Through indoor uniaxial pressurized rockburst experiments,supplemented by high-speed cameras to capture phenomena and acoustic emission system to detect internal damage,etc.,combined with Flac3 D for tunnel section simulation,the best pre-stressed anchor active support parameters arrangement scheme is proposed.The main research contents and conclusions are as follows.(1)ANSYS numerical simulation combined with multivariate analysis was used to perform ground stress inversion for the whole tunnel line,and the ground stress regression function was obtained for the tunnel site area.It was found that the stress field distribution law for the whole line of Dagangshan tunnel was dominated by self-weight stress,and the maximum self-weight principal stress was as high as 30 MPa,and the change of each stress component was highly similar to the change curve of burial depth,and a sudden drop of stress value occurred at its fault and lithological partition.At the same time combined with the rock burst criteria to increase the stress release rate of the way comprehensive prediction of the entire excavation may produce rock burst intensity,found that the tunnel excavation stress increases with the increase in stress release rate,most of the line may occur in most areas of minor or moderate rock burst,very little burial depth above 1000 m may appear strong rock burst,its mileage up to 1.8km.(2)according to the active anchor different pre-stress magnitude and layout spacing design experimental program,high-speed camera to capture the experimental phenomenon,acoustic emission system to collect internal data as the main means of detection,the test block for each condition of experimental pressure,the intensity of rock burst and pre-stress size and anchor spacing changes between the law: pre-stress increases can effectively inhibit the generation of rock burst;spacing reduction on the occurrence of rock burst phenomenon influence is small,but the formation of internal damage has a suppressive effect,and finally according to the spread of damage recommended the best anchor arrangement spacing is less than 20 times the diameter of the anchor rod is preferred.(3)On the basis of rock burst prediction,through Flac3 D numerical simulation,establish tunnel section model under different rock burst levels,adjust the active anchor support pre-stress value,layout spacing,rod length and other key parameters,and combined with the super pre-stress anchor analysis of the combined support system on the effect of rock burst suppression,and finally concluded that: pre-stress increase,spacing reduction,rod length increase can effectively It is concluded that the increase of prestressing force,the decrease of spacing and the increase of rod length can effectively reduce the maximum principal stress and energy value of the surrounding rock,the singlering pre-stressing anchor has a certain inhibiting effect on rock burst but cannot effectively reduce the intensity and grade of rock burst,the pre-stressing active support parameters can be optimized while ensuring the inhibiting effect of rock burst,and finally the best pre-stressing active anchor support scheme is proposed for different grades of rock burst section in Dagangshan Tunnel. |
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