Study On Rock Mass Sound Wave Signal By Wavelet Time-frequency Analysis Theory

Acoustic detection technology based on elastic wave propagation theory, the main research acoustic propagation law and in the rocks formed by structure surface acoustic wave impedance interface, the influence of communication engineering geological evaluation, especially for the stability evaluation to provide important basis. Present acoustic detection technology, mainly using rock, its kinematics characteristic parameters, the longitudinal velocity to use less dynamic characteristics.In order to further waves of various parameters on the comprehensive analysis, this paper selects a hydropower station, using acoustic signals measured area and the programming of Matlab software for the wavelet time-frequency analysis, this study results:(1) of acoustic detection signal wavelet decomposition and reconstruction, the low frequency noise reconstruct signal analysis, through a series of signal-to-noise evaluation standard to confirm the best decomposition layers and suitable for the optimal acoustic detection signal wavelet base.(2) acoustic detection signal is essentially a the non-stationary signal, acoustic signals through complex geotechnical media, there are various frequency interference wave, the composition of the interference of the signal superimposed for accurate judgement of the first time difficult. Using the wavelet analysis of measurement noise acoustic detection signal processing in a certain extent, reduces the noise signal waveform and interpretation of early, so as to improve the accuracy of the test.(3) according to the principle of the ultrasonic detection signal, the waves in the medium, the first by the media and absorption and scattering of attenuation, secondly in different medium refraction and will happen boundary. Due to the different medium attenuation coefficient of different and different interface refraction wave and reflection wave, acoustic signals of different paths of different frequencies. Using the optimum wavelet decomposition of rock sound test signals into different frequency channel wavelet vectors, and on the third floor frequency spectrum signal reconstruction result analysis, extraction, the maximum amplitude, phase spectral parameters.Based on different rock mass of acoustic detection signal spectrum analysis, acoustic signals that the dynamic parameters (energy, contents, phase) can be very good reflects the weak layers of rock joints and fractures and position. Combining velocity value of multi-parameter comprehensive analysis can effectively improve the accuracy and reliability of the explanation.