| This paper takes the three mine seismic events in the Fankou lead-zinc mine as the background,and makes comprehensive use of research means and methods such as engineering geological investigation,numerical simulation,and on-site blasting vibration monitoring,etc.The main research contents and results of the paper are as follows.(1)The mining and filling situation in the area where the mine earthquake occurred were investigated,and the causes of the mine earthquake as well as the possible high stress areas and reasons was analyzed.(1)In the-500m～-600 m N4#S area,stress concentration was caused by stress transfer in the stoping process.The surrounding rock in the area between sublevel drift and 214 A ore body became the support structure of overlying rock mass,which also produced stress concentration.(2)The "cantilever beam" structure was formed during the mining process of 214 a ore body.Under the condition that the roof of the lower goaf is not effectively supported by the filling body,the maximum compressive stress could reach 129.76 mpa,and it is very likely to cause ore shock due to material failure and rock fracture.(3)Macroscopic stress analysis was carried out for the F3 fault,and the conditions for the occurrence of sliding and mine seismic were that the positive stress value was less than5.227 MPa and the critical depth was 2162 m.(2)The model of 214 a ore body and fault was constructed and statically calculated,and the stress field along the ore body strike,vertical ore body strike stress field,fault stress field and displacement field were analyzed.A numerical model of N2# transverse drift’s profile was established,and the displacement field and stress field before the 209 a ore body were mined were calculated and analyzed.The results show that:(1)Large areas of positive stress less than 5.227 MPa occur on the faults at N2#,N4#,and N6#,and it can be determined that there is fault activation,which will lead to fault slip-type mine tremor.(2)In the area of N4#S,the maximum compressive stress in the vertical direction reaches 35 Mpa.(3)The stress is concentrated between below the-550 m third segment to the-550 m first segment.The latter two have higher risk of gravity-induced ore pillar and rock wall destabilization type mine seismicity.(3)The vibration acceleration decay formula and the main frequency of blasting vibration were obtained by monitoring and analyzing the vibration acceleration in the near area of blasting.The vibration acceleration corresponding to different distances and section charge amounts were calculated and applied to the model for calculation,and the simulation results showed that: the amount of fault slip was positively correlated with the length of 214 a ore body caved and the blasting vibration amplitude;when blasting the 209 a ore body,the east and west sides of the tunnel were more easily damaged than the east gang.Both sides of the gang are more easily damaged than the top and bottom plates,and the displacement values of the west gang are larger than those of the east gang;after the explosive quantity of a single section is increased to 100 kg,obvious tensile damage occurs around the quarry.(4)The impact of mining the 209 a ore body on its adjacent area is studied,and three mining and filling options are proposed.According to the above simulation results,the control measures of mine seismicity are proposed for the morphology of the ore body and tectonic stress characteristics of the Fankou ore body on various aspects such as mining method,quarry layout and retrieval sequence,and blasting vibration reduction. |
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