Research On Analysis Method Of Channel Waves Propagation Characteristics In Coal-Bearing Strata

Based on the National Natural Science Foundation of China project "Surface detection theory of coal seam reflection trough based on continuous source",this paper studies the analysis method of channel waves propagation characteristics in coal-bearing strata.It is difficult to analyze the received channel waves when coal seam detection.On the one hand,the energy gradually decays with the extension of the propagation distance.On the other hand,it is faced the conversion of the wave pattern and the train elongation,resulting in serious distortion of the receiving signal.Aiming at the above problems,this paper analyzes the reflection and transmission of the elastic wave at the coal-surrounding rock based on the study of channel waves formation and classification,the reflection and transmission coefficients of P wave,SV wave and SH wave are derived.Then the attenuation problem is analyzed,and the relationship between the amplitude and the propagation distance is derived.In order to construct the parameter of channel waves propagation model,the effects of shear wave velocity,surrounding rock density,coal seam thickness and signal source position are analyzed.The simulation model parameter is determined by analyzing the channel waves waveform,spectrum and energy imaging.By analyzing the coal seam channel model,the relationship between the source and the original seismic records and seismic correlation records is derived.When the source signal or it is autocorrelation function is close to the impact signal,the main sidelobe ratio is large and the sidelobe decays fast.At that time,the coal seam characteristics can be analyzed by original seismic records or seismic correlation records.It is decided to use the periodic pseudo-random signal as sources signal.and the binary fourth-order pseudo-random scan signals and the ternary fourth-order pseudo-random scan signals are simulated and compared,and the correlated wavelet of the ternary fourth-order pseudo-random scan signal is closer to the impulse function.Using the short-time Fourier transform to analyze the received channel waves,it is found that there is spectral aliasing in the received channel waves under the action of the binary fourth-order pseudo-random scan signal source.Interference phenomenon in the receiving channel waves under the action of the ternary fourth-order pseudo-random scanning signal source.The source signal is optimized,and the binary and ternary pseudo-random scan signals are reconstructed by the m-sequence mapping method,which eliminates the spectral aliasing and interference of the channel slot wave,and provides reference for the channel waves amplitude compensation and analysis.Finally,the fault and gangue model is simulated by using the ternary pseudo-random scan signal.The results show that the channel waves has a serious attenuation after the fault propagation,but there is no spectrum aliasing or interference in the spectrum.