Analysis Of Channel Wave Propagation Characteristics In Complex Coal Measures

This project is derived from the 2017 annual open fund project of the National Key Laboratory Breeding Base of the Ministry of Mine Disaster Prevention and Control:"Study on the Fine Exploration Method of Coal Mine Underground Channel Wave Based on Spreading Frequency Continuous Source".This project aims to analyze the influence of complex coal seam small structures on the characteristics of channel wave propagation,and provide basic theoretical support for the detection of channel waves in actual coal-bearing strata in fund projects.Based on the theory of slot wave propagation and communication-related theory,the propagation characteristics of the channel wave in the complex coal-bearing strata with geological anomalies are studied for the channel characteristics of the coal-bearing strata and the geological characteristics of the scouring zone and the old-fashioned zone in the coal-bearing strata.A specific analysis was carried out.Mainly completed the following work:(1)Firstly,the paper studies the related aspects of the channel wave at home and abroad,and introduces the background and significance of the topic.And introduces the related theories of the formation and classification of channel waves.The characteristics of the channel wave in coal-bearing strata are analyzed,and the small structures contained in the coal-bearing strata are briefly introduced.It provides a theoretical basis for the analysis of the propagation characteristics of the channel wave by establishing a three-dimensional equivalent medium geometry model.(2)Analyze the typical geological structures in the coal seams such as the scouring zone and the old airspace,and the causes of their formation,and their geological channel characteristics,and determine the model parameters.Analyze the characteristics of the source signal of the coal seam model,and select the Rake wavelet as the source signal of the model.(3)Analyze the influence of the scouring belt on the channel wave propagation.In the COMSOL Multiphysics,a three-dimensional equivalent medium geometry model of the coal-bearing strata without the scouring zone and a geometric model of the equivalent structural equivalent geometry of the complex coal seam with the scouring zone are established.The finite element simulation of the propagation of the channel wave in the two models is carried out and its propagation characteristics are analyzed.The coal stratum model is introduced and theoretically deduced,and the rationality of the model is verified.The explosive source was simulated with a Lex wavelet at a frequency of 100 Hz,and the vibration signals of the line points were excited and obtained in the two models.Using MATLAB to obtain the amplitude variation,the channel wave receiving signal map and the total elastic strain energy change and amplitude frequency change of the coal seam of the two models,and transform the signal into the f-k domain to observe its power variation,and compare the presence or absence of abnormal structural equivalent medium.The difference of the channel wave propagation in the geometric model of the equivalent medium is compared with the abnormal structure,and then the influence of the scouring belt on the channel wave propagation is analyzed.(4)Analyze the impact of the old airspace on the wave propagation.In the COMSOL Multiphysics,the three-dimensional equivalent medium geometry model of the coal-bearing strata without the old empty space and the geometric model of the equivalent coal-body structure with the old empty space are established.The finite element simulation of the propagation of the channel wave in the two models is carried out and its propagation characteristics are analyzed.Similarly,the Rake wavelet is used to excite and obtain the vibration signals of the line points in the two models.Using MATLAB to obtain the amplitude variation,the channel wave receiving signal map and the total elastic strain energy change and amplitude frequency change of the coal seam of the two models,and transform the signal into the f-k domain to observe its power variation,and compare the presence or absence of abnormal structural equivalent medium.The difference of the channel wave propagation in the geometric model of the equivalent medium is compared with the abnormal structure,and then the influence of the old space on the channel wave propagation is analyzed.