| The study of stope rock fracture is the basic work to prevent and control dynamic disasters and ensure safe and efficient mining of mines.In order to study the fracture characteristics of stope strata,this paper uses the methods of theoretical analysis,similarity simulation and field examples.The acoustic emission system is used to continuously record the internal activities of stope strata in the similarity simulation experiment,and the fracture characteristics of stope roof and floor slate are obtained by the inverse analysis of acoustic emission data.The correctness of acoustic emission inversion of rock fracture characteristics in the similarity simulation experiment is verified by the example of field microseismic monitoring.The main conclusions are as follows:(1)The similar simulation experiment and acoustic emission layout scheme are designed.Acoustic emission monitoring is applied in the similar simulation experiment.Before the test,the noise test,connectivity test,lead breaking test and wave velocity of the material are measured.In order to eliminate laboratory and other noise interference,acoustic emission documents are filtered.(2)The validity of the theoretical model of “the three-zone structure loading model” is verified by similarity simulation and acoustic emission technology.According to the theory of “the three-zone structure loading model” model,it is calculated that the leading influence range of the theoretical model is 29.47 m.The similar simulation experiment shows that the leading stress peak is about 30 m in front of the coal wall,and the acoustic emission inversion shows that the leading influence distance is 35～40m in front of the coal wall,which verifies the effectiveness of the“the three-zone structure loading model” analysis method.(3)The activities of the first pressure and periodic pressure of the main roof make the acoustic emission events periodic.The event distribution is that the density of low-level rock stratum is large and the density of high-level rock stratum is small,indicating that the damage degree of mining to different ranges of rock stratum is different,the fracture degree of low-level rock stratum is large and the fracture process of high-level rock stratum is small.The roof falls behind,and the breaking load acts on the bottom plate.The distribution of acoustic emission events presents a layered failure form.The events are relatively active in the range of about 14 m below the bottom plate.(4)The microseismic monitoring results show that with the advance of the working face,the development of microseismic events in height is periodic,and the acoustic emission inversion results have similar characteristics,which verifies the correctness of acoustic emission inversion of rock fracture characteristics in similar simulation experiments.(5)The waveform characteristics of acoustic emission when the floor rock is broken are obtained.When the degree of rock failure activity is small,the waveform amplitude is small,generally below 120 mv,and there are two consecutive waveforms.The first waveform is shorter than the second one,and the peak frequency is about140 KHz.When the degree of rock failure activity is large,the waveform amplitude span is between 120mv～4v,and there are no two continuous waveforms,and the peak frequency is between 130～150KHz.The experimental results show that the use of acoustic emission technology can well describe the fracture characteristics of stope strata in similar simulation experiments,and provide a reference for the field study of stope strata movement.Figure 61 Table 11 Reference 85... |
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