Research On The Effect Of Local Risk Reduction Of Drilling And Splitting Of Surrounding Rock With Rock Burst Tendency

Rock burst de-danger and effect evaluation have become the key problems in deep engineering safety construction and disaster prevention and reduction.In order to solve the local danger of rock burst,a method of splitting the pressure relief borehole at a certain Angle is proposed.Based on theoretical analysis,laboratory test and numerical simulation for the research method of combining combined with XRD,acoustic emission monitoring,stress and strain monitoring,video and other means,The research on the rock burst release effect under the condition of different splitting angles and no splitting in the borehole was carried out,and reproduces the whole process of splitting failure of the surrounding rock of the high-stress roadway,and obtains the following results.(1)The composition of gabbro specimens was analyzed by XRD test,and the results showed that gabbro mainly consists of pyroxene and plagioclase.At the same time,the gabbro is analyzed and judged by combining two kinds of rock burst liability determination indexes,and it is proved that gabbro has rock burst liability above medium.(2)Through four groups of gabbro specimens for biaxial compression test,the results show that compared with the simple pressure relief hole,the control of the process of local de-danger evolution of surrounding rock containing 0 and 45 degree seam is changed from the two sides of decompression holes to the end of the split fracture,which expand the decompression area,and the decompression hole work together with the crack.The nonlinear characteristics of the relation curve between stress and vertical strain before peak are enhanced.The energy dissipation in front of peak are enhanced,the integrity of the surrounding rock is reduced to a greater extent,and the effect of decompression is obvious.The process of local de-danger evolution of surrounding rock containing 90 degrees split cracks is still controlled by the two sides of decompression holes.The local de-danger effect of 0 degree seam is the best which pre-peak energy release ratio reached 85.70%,followed by 45 degrees,and 90 degrees is poor.(3)the FLAC3 D numerical simulation was carried out based on the laboratory test and field.The results show that,under the same condition,the non-uniformity of surrounding rock deformation is the biggest around the pressure relief hole and the crack of zero degrees,and the energy is easily dissipated by local damage,the non-uniformity of surrounding rock deformation under the condition of cracks of 90 degrees and non-cracks is the smallest,almost uniform,and it is difficult to dissipate energy by local damage and fracture;When the crack angle is from 0 to 45,the plastic zone begins to sprout from the tip of crack tip and develops along the direction of maximum principal stress,the plastic zone from the face to the bottom of the hole shows an approximate cone-shaped contraction in the direction along the axis(y axis)of the pressure relief hole,that is,from the bottom of the hole to the face of the surrounding rock,the plastic zone increases continuously with the increase of thecrack angle,the range and volume of plastic zone of surrounding rock decrease accordingly.(4)Based on the analysis of rock burst surrounding rock from the integrity perspective,when the integrity of rock burst reaches a relatively broken level,the sudden release of energy can be avoided,and the rock burst tendency can be greatly reduced.It can be considered that the local rock burst effect has met the requirements.Then it is determined that the depth of risk reduction of rock burst is used as the index to evaluate the effect of risk reduction.According to the fracture evolution characteristics of surrounding rock in the borehole range,the plastic zone is simplified reasonably.Then,quantitative analysis and mathematical derivation were carried out on the determination of the depth of risk reduction of rock burst by using the integral idea,and the calculation method and derivation formula for determining depth of risk reduction of rock burst were presented.