Research on Propagation Characteristics of Infrasound Waves in Coal Seams and Roadways in Complex Spaces

Author:Jia Bing

Supervisor:wei jian ping


Degree Year:2018





Grasping the propagation characteristics of infrasound caused by the rupture of coal in coal seams and roadways in complex spaces is of great significance for studying the effective propagation distance of infrasound in different coal and the effective acquisition of infrasonic signals,and evaluating the feasibility of applying infrasonic waves in coal mine disaster prediction.In order to determine the frequency and amplitude characteristics of infrasound caused by rupture of coal,the method of combining theoretical analysis and simulation is used to optimize the improved EMD filtering method and Hilbert transformation frequency analysis method.Then,an experimental platform was set up to test the infrasound and acoustic emission characteristics during the loading process of coal sample,and the frequency and amplitude characteristics of infrasound in the sample deformation and failure process were determined.At the same time,the characteristics of precursory acoustic response of coal sample destruction were determined.Finally,from the energy point of view,taking the damage as the intermediate variable,the relationship between the size of the damaged coal sample and the infrasound amplitude was established.Based on the test results of small size coal samples,the characteristics of the infrasound amplitude of large size coal samples were determined.In order to study the infrasonic attenuation characteristics caused by fluid flow in the coal,the method of theoretical analysis and experimental testing is used to analyze the fluid coupling decay mechanism.Then,based on the fracture characteristics of coal and rock mass pores,the coal body is divided into different regions according to the difference of attenuation mechanism of different fluids.The attenuation coefficient models suitable for different regions are respectively constructed,and the flow decay coefficient model of fluid flow is established based on the weight ratio of different regions.By setting up the subsonic attenuation coefficient test platform,the infrasonic attenuation coefficient of the coal samples in the study area was tested,and compared with the theoretical calculation results,the accuracy of the model was evaluated.Finally,the model of synthetic acoustic attenuation coefficient suitable for different coal and rock mass conditions was determined.The mechanism that causes the difference of the infrasound is analyzed,and the principle of choosing the location of the infrasound and the way of collecting is determined under different roadway layout conditions.Using numerical simulation method,taking the infrasound amplitude and frequency characteristic of the rupture of coal as the main basic parameters,taking two typical roadway arrangements as examples,the propagation attenuation model of the infrasonic wave in the coal body is solved.According to the calculation results,the characteristics of different acoustic pathways,different acquisition methods and different positions are determined.Finally,a method of acquisition of the infrasound suitable for other complex space conditions is determined.This provides theoretical guidance for studying the feasibility of applying sub-acoustic forecasting technology to mine disaster prediction.