| The rockburst disaster is destructive and harmful.In China,85% of the coal mine rockburst disasters occur in the mining roadway.The main reason is that the superposition stress of the coal and rock mass in the near field high stress area of the roadway exceeds its strength limit and the accumulated elastic energy and strain energy are released in an instant,which leads to the intense destruction of the roadway.Therefore,the two ways to prevent and control the rock burst roadway are to relieve the high stress concentration of the surrounding rock of the roadway or to strengthen the support to improve the ability of the surrounding rock of the roadway to resist the impact damage.The effect of coal seam blasting is obvious and adaptable,but the damage effect of coal seam blasting will destroy the integrity of surrounding rock,reduce the bearing capacity of surrounding rock,and weaken the impact resistance of support structure.From this point of view,"blasting pressure relief" and "support and reinforcement" are both contradictory and unified.How to achieve the "synergistic effect" of the two is a very important research topic.In this paper,field test,numerical simulation,theoretical analysis and other research methods are used to analyze the mechanism of coal seam blasting pressure relief and erosion reduction and the mechanism of damage to the surrounding rock and support body of the roadway.The evaluation method of the surrounding rock of the roadway damaged by blasting is constructed.The reconstruction technology of the bearing structure of the surrounding rock of the damaged roadway is proposed,and the realization path of blasting pressure relief and support reinforcement coordinated erosion prevention is planned.The main research results are as follows:(1)The mechanism of pressure relief and erosion reduction in coal seam blasting is studied.Based on the characteristics of blasting zones in coal seam,the mechanism of pressure relief and erosion reduction in coal seam blasting is summarized.The results show that coal blasting can reduce the mechanical properties of coal,improve the impact tendency of coal,adjust the peak distribution of transfer and concentration stress of roadway bearing structure,form dissipation impact energy transfer in pressure relief area.That is to say,the mechanism of coal seam blasting pressure relief and erosion reduction can be summed up as "modification-load reduction-energy consumption ".(2)This paper analyzes the damage effect of coal seam blasting pressure relief on roadway support.The stress wave of coal blasting causes the surrounding rock around the roadway to loosen and damage,the strength of the coal in this area decreases,and the bearing capacity decreases;the blasting pressure relief of coal seam destroys the original bearing structure of the roadway,and reduces the stability of the bearing system of the surrounding rock;under the blasting pressure relief,the anchoring capacity of the anchor decreases,the local anchor fails,and the capacity of the supporting system of the anchor of the roadway decreases;after the blasting pressure relief,the surrounding rock of the roadway decreases The fracture of surrounding rock increases,the integrity of surrounding rock decreases,and the accumulated deformation of roadway increases.The damage effect of coal seam blasting pressure relief on the surrounding rock of roadway support can be summarized as: "surrounding rock degradation-structural instability-support attenuation-roadway deformation".(3)The dynamic response characteristics of surrounding rock under the action of blasting pressure relief are revealed.By using pasat-m portable microseismic system,the propagation rules of different blasting stress waves and the dynamic response characteristics of surrounding rock of roadway are measured.The results show that the duration of high-energy blasting vibration is longer than that of low-energy blasting,and the main frequency and amplitude of vibration of blasting side,roof and non blasting side have different linear relationship with the distance to the source.When evaluating the damage of blasting pressure relief to the surrounding rock of roadway,three indexes of amplitude,frequency and duration of blasting vibration should be considered.(4)The damage mode of surrounding rock of roadway under the action of blasting pressure relief is analyzed.Based on the blasting vibration parameters of roadway surrounding rock obtained from field measurement,the numerical model of roadway blasting vibration is established by FLAC3 D numerical simulation method,which reveals that the main failure mode of roadway surrounding rock under blasting vibration is shear failure;the near-field surrounding rock stress level increases slightly in the process of blasting vibration,and the stress of roadway surface surrounding rock decreases after the end compared with that before blasting.(5)The evaluation method of coal seam blasting damage roadway and the key technology of anchor bearing structure reconstruction are put forward.According tothe elastic mechanics and wave dynamics,the extension characteristics of the plastic zone of the damaged roadway are analyzed,and the evolution process of the deformation and instability of the roadway is revealed.The support evaluation method of the damaged roadway is established,and the remodeling principle and key technology of the anchor bearing structure are put forward.The results show that a dynamic stable plastic boundary is formed in the surrounding rock after the excavation of the tunnel,and a secondary dynamic stable plastic boundary is formed by the expansion of the primary dynamic stable plastic boundary caused by the blasting stress wave.When the blasting area enters the influence range of the leading support stress,the surrounding rock of the tunnel continues to expand outward to form a three-time dynamic stable plastic boundary.Based on the comprehensive consideration of the damage of surrounding rock expansion and the resistance of bolt working,a seven level classification standard of blasting damaged roadway is proposed.On this basis,the principle of remolding the bearing structure of surrounding rock with full section support,unsymmetrical local key reinforcement,shock-resistant components and grouting modification is put forward.(6)Based on the strength theory,combined with the "dynamic stress hardening effect" and "one-way three-way hardening effect" of coal body,a criterion for the occurrence of tunnel rockburst is established.The necessary condition for the main stress around the surrounding rock to cause impact is that it exceeds the one-way compressive strength of coal rock,that is Based on the fact that the seismic CT in-situ detection reveals the distribution characteristics of static stress in the working face,the risk assessment model of rockburst is established with the abnormal coefficient of wave velocity AC and gradient coefficient of wave velocity GC as the main factors,and the methods of risk assessment and risk area determination are proposed.(7)The key technology of coal seam blasting pressure relief and support reinforcement is formed.During the dangerous construction of rock burst tunnel,the blasting pressure relief and support reinforcement should be considered together.The positive effect of blasting pressure relief "modification load reduction energy consumption induced scour" should be brought into play,and the negative effect of blasting pressure relief "surrounding rock deterioration structural instability support attenuation tunnel deformation" should be minimized.When the negative effect is beyond the allowable range,the key technology of damaged roadway bearingstructure reconstruction is used to improve the impact resistance of the support structure,and finally achieve the coordinated impact prevention of precise blasting pressure relief and high impact toughness anchor mesh cable support.(8)Good results have been achieved in the field practice of blast relief and support reinforcement combined with anti scour.This paper analyzes the characteristics of high self weight stress,strong structural stress and sustained growth of lateral support pressure behind the goaf.Using seismic wave CT in-situ detection technology inversion,the tunnel impact risk index C = 0.5 ~ 0.7 is obtained.The blasting pressure relief support reinforcement coordinated anti scour technology of "coal seam pre pressure relief-mining disturbance reduction-tunnel full section reinforcement support" is developed.The field application is successful and the monitoring stress is successful There was no sudden increase in microseismic energy and frequency. |
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