Coal Body Vibration Natural Frequency Response Characteristics And Influencing Factors Of Research

When mining deep coal seam permeability is low,difficulty increases the permeability of coal seam,the key problem of restricting coal seam gas extraction,with the development of the technology of low permeability increases the permeability of coal seam,in recent years,the technique of vibration wave excitation resonance increases the permeability of coal,the advantages of this technology is that the frequency of the vibration wave when close to the natural frequency of coal and rock,coal and rock itself incentive resonance,Thus,the fracture effect and permeability of coal rock are significantly improved.In order to realize the application of coal resonance infiltration technology excited by vibration wave,the characteristics of natural frequency response of coal vibration and its influencing factors must be explored first.In order to determine the influencing factors of coal vibration natural frequency,firstly,based on vibration mechanics and structural dynamics,single-dof and multi-dof coal vibration models were established,and the vibration response characteristics of coal were analyzed theoretically.Then,through the comparative analysis optimization "tapping" as coal vibration natural frequency test method,from the installation of sensors,the choice of the ways of coupling,the sampling frequency to set three aspects to consider and determine the coal body vibration signal acquisition method,at the same time optimizing the hanning window of the vibration signal processing to improve the reliability of vibration natural frequency test results,It lays a foundation for the subsequent analysis of coal natural frequency test results.The natural frequency test platform was built independently,and four experimental schemes were designed to discuss the influence of bedding,moisture,size and coal rank on the natural frequency of coal vibration.The natural frequencies measured parallel to the stratified plane are larger than those measured perpendicular to the stratified plane.The natural frequency of saturated coal sample is lower than that of dry coal mainly because the density of saturated coal sample increases,the elastic modulus and uniaxial compressive strength of saturated coal sample decrease obviously.The natural frequency of coal body with the edge length of 30 mm,50mm and 100 mm decreases.The difference of natural frequency of coal with different rank is mainly due to the difference of its mechanical parameters.The correctness of the theoretical analysis is verified by comparing the experimental results with the theoretical analysis conclusions.Based on the measured physical and mechanical parameters of coal and the natural frequency test results,the acceleration response of single coal is solved by using the harmonic response analysis module of ANSYS Workbench finite element software.To simulate the different exciting force,different size,different mechanical parameters of single coal vibration acceleration response characteristics,it is concluded that the peak acceleration response of the frequency is the natural frequency of the coal,the size of the exciting force of vibration natural frequency of coal is no effect,but the vibration response of the peak value increases with the increase of exciting force;The larger the size,the smaller the natural frequency and response peak value of coal.The natural frequency is determined by its mechanical parameters.The greater the elastic modulus and stiffness,the greater the natural frequency and the smaller the vibration response peak value.Based on the analysis of the simulation results of single coal body,the 3d numerical model of coal-rock complex and the complex coupled with coal body and gripper was established to solve its acceleration response,and the natural frequency of coal body in the complex was higher than that of single coal body.The natural frequency of granite is the largest,followed by that of coal-rock complex,and the natural frequency of single lignite is the smallest.When the coal is coupled with the gripper,the stiffness of the coal increases,so does the natural frequency.It provides a reference for further research on the technology of coal rock resonance enhanced permeability excited by vibration wave.