| The acquisition of mechanical parameters of rock mass is one of the basic work of rock mass engineering,several rock masses were selected randomly to carry out in-situ tests on deformation parameters of rock masses and selected the surfaces with different crushing degrees to carry out the stress wave propagation test of rock mass in the gold mine goaf of the Double flags.A rock strength test was also carried out in the laboratory in which rock mass mechanical parameters was obtained by wave velocity method,and thus used the FLAC3D software to analyze the safety and stability of goaf.Here are the results of the study:(1)According to stress wave longitudinal wave attenuation coefficient curve of the four representative test points in the gold mine goaf,they were analyzed from frequency range 0-2000Hz which was divided into 0-800Hz and 800-2000Hz.From which acquired propagation characteristics of elastic longitudinal wave of engineering rock mass with different wave velocity:1,The longitudinal wave has high frequency and high attenuation when the wave velocity of the rock mass is high.2,When the wave velocity of the rock mass is large,the attenuation coefficient is sensitive to the response of the frequency.When the frequency of the longitudinal wave is about 200Hz and 2000Hz,the amplitude of the longitudinal wave attenuates rapidly and the attenuation coefficient is large.But when it is between 200Hz and 2000Hz,the attenuation coefficient of the longitudinal wave has little change with the frequency,which is close to a linear relationship.Similarly,it is the same for 300Hz and 400Hz.(2)The mechanical parameters of rock mass calculated by the wave velocity method of rock mass are cohesive force c=0.66Mpa,internal friction angle ?=45.0°and E.Hoek Suggestion which also means the mechanical parameters of rock mass obtained from the parameters of the Hoek-Brown strength criterion to the Mohr-Kulun strength criterion parameters are cohesive forces c=1.lMpa,internal friction angle ?=38.74°,according to the analysis of the comparison of the two results,the absolute difference between the cohesion value c obtained by the two methods is 0.44,the absolute difference between the angle of internal friction angle is 6.26,the two methods estimate the difference of cohesion value c,and the value of the internal friction angle is more conservative because of e.h.oek's suggestion,the calculation of the value of the internal friction angle is better than that of the project Therefore,the mechanical parameters of rock mass obtained by this method are numerically simulated.(3)Through numerical simulation,it can be concluded that the two goaf is in a stable state and some pillar and roof have a certain plastic yield;The subsidence and deformation of the two mined areas are small,the maximum value is above the No.1 goaf,and the size is 3.44mm.The mining of No.2 goaf made the deformation of the dangerous area increased,1#pillar added 0.0439MPa,2#pillar added 0.0127MPa and 3#pillar added 0.0439MPa.Therefore,the mining of goaf No.2 is unfavorable for No.l goaf,but the influence was limited.Conditions for different thickness(thickness is 4 m,5 m,6 m),analyze the no.2 mined-out area yield condition can get mined-out area as a whole is safe,but with the reduction of thickness of roof tensile yield in a large radius,the adverse effects on local security. |
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