Correlation On Frequency Characteristics Of Acoustic Emission With Stress State Of Bump-prone Rocks

The occurrence of rockburst is determined by many factors, including physical and mechanical properties of the rock mass, stress condition where the rock is, and so forth. Burst potential is the inherent property of the rock mass as well as is also the internal and the necessary reason of disaster. Acoustic emission(AE) technique is an important method for monitoring and early warning of rock burst. Rock internal state changes, inversion of the damaging mechanism of rock and degree of destroying are able to be inferred through the analysis of signal of AE under different loading conditions. Then, it could provide evidence for identifying disasters and early warning of rock burst.Laboratory experiments on the characteristics of AE frequencies and basic parameters in different frequency channels of different bump-prone rocks under different loading conditions in this paper. The main research contents and achievements include:(1) Laboratory experiments on the characteristics of bump-prone granite specimens under uniaxial compression, triaxial compression, uniaxial compression and triaxial compression of cyclic loading and unloading were carried out. The characteristics of burst potential in different confining pressures were analyzed. The relationship between damage energy release rates and damage variables were studied. The burst liability of bump-prone granite of the lowest axial stress level was studied.(2)Based on bump-prone siltstone tests of AE under uniaxial compression of loading and unloading, the load-unload response ratio (LURR) of AE, elastic modulus, and deformation were analyzed. We can improve accuracy for estimating and predicting the critical state of rock mass by using the changes of the multi-factor LURR in practical application.(3)Laboratory experiments on the characteristics of AE in high and low-frequency channels of bump-prone granite specimens under different confining pressures of cyclic loading and unloading were carried out. The relationships between the time with stress and AE cumulative counts were analyzed. On the basis, the characteristics of AE irreversibility in rock were studied. Then inverse fast Fourier transform (IFFT) was used to denoise the AE signals at Kaiser Points and the characteristics of spectrums in denoised signals were analyzed with fast Fourier transform (FFT). The characteristics before the major fracturing in rock were studied. The results of the dominant frequencies at Kaiser Points provide evidence for the damage and failure of bump-prone rock.(4) Laboratory experiments on the characteristics of AE of bump-prone granite specimens under different confining pressures with cyclic loading and unloading were carried out. The characteristics of the energy distribution in frequency bands at Kaiser and adjacent points are studied by means of the wavelet packet analysis technique. And the relevant fractal dimensions at Kaiser and adjacent point’s energy are obtained by using G-P algorithm. The results of Kaiser Points provide the evidence for the damage and failure of bump-prone rock.(5) Laboratory experiments on the characteristics of AE frequencies and basic parameters in different bump-prone rocks under triaxial compression and uniaxial compression were carried out. The characteristics of AE frequencies, dominant frequencies, counts, energy, and hits etc. At different stages in these rocks. The results provide the evidence for estimating and predicting rockburst.(6) A multi-band AE dominant frequencies recognition criterion model which is based on the quantitative relationships between proportions of frequency bands and stress was established. The characteristics of AE frequencies under triaxial compression and uniaxial compression were analyzed. And the multi-band AE dominant frequencies recognition criterion model of bump-prone granite was established.