| As the mining depth of underground mines continues to increase,rockburst disasters become more frequent,and the roadway rockburst problem needs to be solved urgently.Aiming at the problem of frequent rock burst disasters in deep roadway and the poor effect of single rockburst control method,a hole-bolt-filling collaborative method(hereinafter referred to as H-B-F collaborative method)for rockburst relief in deep roadway is proposed,which combines three methods: borehole pressure relief,bolting and flexible material filling.Through laboratory test,numerical simulation,theoretical analysis and engineering field examples,the collaborative danger relief effect of H-B-F in rockburst in straight wall arch roadway was studied,and the following results and conclusions were obtained.(1)The composition analysis,rockburst tendency test and ultrasonic test of the selected granite samples are carried out,and the main mineral composition of the samples is determined.The test results show that the samples have medium or above rockburst tendency and good uniformity,which can meet the requirements of the internal causes of rockburst.(2)Biaxial compression tests were carried out on four groups of granite samples(straight wall arch tunnel sample,pressure relief hole sample,H-F sample and H-B-F sample),and comprehensive comparative analysis was carried out by ultrasonic testing,stress-strain monitoring,acoustic emission monitoring,high-definition camera key frame analysis and other methods.The results show that: After the construction of the pressure relief hole,the maximum load that the sample can bear decreases,and the cracks on both sides of the pressure relief hole penetrate the sample is the main cause of the overall failure,and the pressure relief hole plays a key role in controlling the fracture evolution of the surrounding rock;After using H-B-F collaborative method,the spalling and ejection of the surrounding rocks on both sides of the roadway are controlled,and the overall strength and residual strength of the sample are improved;The construction of the pressure relief hole will move the energy release forward,and the energy release ratios of the straight wall arched roadway samples,pressure relief hole samples,H-F samples,and H-B-F samples when reaching the peak value are 57%,24%,25%,and 24%,respectively.Filling with flexible material and installing bolts have basically no effect on the pressure relief effect of the pressure relief hole.(3)The cushioning and supporting effect of the flexible filling material was simulated by using the high-performance discrete element software Mat DEM,and the particle dynamics in the whole process of its fracture evolution were analyzed.The results show that the flexible material plays a buffering and supporting role in the process of surrounding rock failure,the ejection and avalanche of rock particles are significantly reduced,and the flying speed of rock particles is reduced by more than30%,which reduces the damage of ejected rock particles.(4)Using FLAC3 D software,the indoor test sample scale model and the field large-scale numerical model were respectively established and simulated,the results showed that: There will be uneven deformation at the pressure relief hole,which will easily lead to local damage and rupture of the surrounding rock,and dissipate elastic strain energy;The phenomenon of stress concentration at the pressure relief hole is obvious.In the large-scale simulation,the maximum principal stress value of the H-BF model can be increased by 134%,which is conducive to stress release;In the largescale simulation,the volume of the plastic zone of the pressure relief hole model can be increased by 4100%.The volume of the plastic zone is relatively large,and the degree of fragmentation of the surrounding rock is relatively high.After using the HB-F collaborative method,the volume of the tensile plastic zone is reduced by about17%.The H-B-F collaborative method maintains the pressure relief level of the pressure relief hole and reduces the risk of rockburst,and at the same time makes up for the problem that the pressure relief hole may cause the support failure of the roadway system.(5)Introducing the damage theory,the damage variable expressions of the surrounding rock of the roadways are established.The damage to the surrounding rock of the roadway evolution was analyzed.The results show that: When no pressure relief and support measures are applied,the damage evolution of the surrounding rock of the roadway is basically the same as that of the shear failure in the open face,which indicates that the fracture evolution is close to the complete shear failure,with large failure strength and high rock burst risk.After the pressure relief hole is applied,the fracture evolution of roadway surrounding rock develops to the direction of complete splitting.After H-B-F collaborative method is used,the damage evolution of roadway surrounding rock is very close to the damage evolution process of the splitting failure of surrounding rock,indicating that its rupture evolution is close to the complete splitting failure,the failure strength is small,and the rock burst risk is reduced.The occurrence of rockburst can be predicted by the evolution process of splitting and shear damage.(6)The calculation formula of tangential stress of roadway surrounding rock is established,and the stress release of roadway surrounding rock is analyzed.The results show that: The H-B-F collaborative method can effectively reduce the tangential stress of the surrounding rock of the roadway,release the stress of the shallow surrounding rock,reduce the accumulation of elastic strain energy,continue to provide effective support after the surrounding rock failure,anchor the broken rock mass,reduce the failure events,and maintain the stability of the surrounding rock of the roadway.(7)The application effect of the H-B-F collaborative method is verified by combining the rockburst cases of two engineering sites,the results showed that: The HB-F collaborative method can significantly reduce the stress value of the shallow surrounding rock of the roadway,and increase the maximum principal stress value by133% and 80%,respectively.The stress concentration area shifts away from the roadway,and the stress concentration degree becomes higher.The volume increase of the plastic zone is 827% and 516% respectively,which is conducive to the release of the elastic strain energy accumulated in the surrounding rock,ensuring the stability of the surrounding rock and reducing the risk of rockburst.The H-B-F collaborative method has a good effect of rockburst relief in engineering field cases. |
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