| The creep property of the rock is one of the main reasons for inducing the destruction of metal mine rocks.Acoustic emission technology is used to predict the creep damage of rock.The key lies in establishing the relationship between the acoustic emission signal and the dynamic evolution law of the acoustic emission source.In this paper,the acoustic emission positioning experiment of red sandstone creep under graded loading conditions is carried out.The moment tensor analysis method and wavelet packet analysis method are used as the main research methods to analyze the acoustic emission activity during the process of rock creep failure under different loading stress conditions.Characteristics,as well as the spatial and temporal evolution of different types of sources and their corresponding main frequency characteristics.On this basis,the quantitative prediction analysis method of rock creep damage based on the main frequency characteristics of different types of sources is studied,and the following research results are obtained:(1)The long-term strength of red sandstone is about 60.8MPa,and its value is about 75% of the average value of uniaxial compressive strength.Under the condition of graded loading,the strain rate of red sandstone during the constant velocity creep stage has an exponential function relationship with the loading stress.(2)According to the duration of creeping acoustic emission,extract the characteristics of the large amount of data in the corresponding acoustic emission waveform file,take the least square method as the center point,and take the length of 1mm as the ball radius,and randomly select 3 points and center on the spherical surface Point,as the four vertices of the quadrilateral,on this basis,according to the moment tensor theory,a simplex algorithm based on the least square method was developed for acoustic emission source location and type identification program,which achieved the source of acoustic emission in the process of creep destruction The programming of positioning and type identification can improve the data processing efficiency of the rock creep acoustic emission test to a certain extent.(3)Compared with the uniaxial compression test,the evolution law of shear,tension and mixed sources during the failure process is shown as the process of developing from the end of the specimen to the middle of the specimen.During the creep failure process of red sandstone,shear,tension and mixed sources are first generated in the middle of the specimen,and then from the later stage of constant velocity creep,the source gradually develops toward the upper and lower ends of the specimen,and at the beginning of accelerated creep The location is again gathered in the middle of the specimen to form a "brief" of the macro-fracture surface,and finally the new source is based on this "brief" during the accelerated creep stage until the macrofracture surface is formed.(4)During the creep failure of red sandstone,the acoustic emission event rate and acoustic emission amplitude increase with the increase of loading stress.At the beginning and end of accelerated creep,the acoustic emission event rate and acoustic emission amplitude both showed a "clustered" increase,and the shape of the curve during the entire accelerated creep phase was similar to the "U" shape.(5)During the staged loading creep failure process,the main frequency range of the red sandstone source is between 0 and 1000 kHz,which is greater than the source frequency range during the uniaxial compression failure process,and the source frequency will increase with the increase of the creep loading stress Increase.Relatively speaking,the shear source shows multi-frequency characteristics during creep failure.(6)The collection and penetration of different types of sources reduce the main frequency of different types of sources,and the main frequencies corresponding to shear,tension and mixed sources can be suddenly reduced to 0~250kHz,as a step loading condition Red sandstone creep failure prediction method. |
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