Seismic Wave Field Characteristics And Imaging Method Of Faults In The Front Of Coal Roadway

It has obvious technical advantages to carry out seismic detection work in underground coal mine.The detail is the following: The detection distance is close and verification is fast.And it can not be disturbed by unfavorable factors on the ground.According to the situation of multi-layer goaf and surface subsidence,it can effectively fill the shortage of ground seismic detection.At present,it is a research hotspot to use mine seismic wave method to carry out faults advanced detection.However,the geological conditions of coal roadway are complex,the faults advanced detection is affected by coal roadway and loose circle of roadway surrounding rock.However,the characteristics of three-dimensional seismic wave field under the condition of coal roadway and loose circle of roadway surrounding rock have not yet been revealed,and it is difficult to accurately construct fault model by conventional migration imaging method.Therefore,it is of great theoretical significance and practical value to study the three-dimensional seismic wave field characteristics and fine imaging methods of faults in front of coal roadways.In this paper,theoretical analysis,numerical simulation and field test are used as research methods.Taking the polarization analysis of complex covariance matrix based on Hilbert transform and statistical vector matrix analysis as the key technologies,this paper studies the formation of a fine quantitative advanced detection of coal roadway faults.The main research results are as follows.(1)The differences of kinematics and dynamics of the effective waves of the normal and reverse faults in front of the tunneling favce are revealed.When carrying out normal fault advanced detection,the diffraction wave of the faulted coal seam in upper wall overlaps with the diffraction wave of the breakpoint and the reflected channel wave in lower wall,and the diffraction wave of breakpoint can not be recognized.When carrying out reversed fault advanced detection,the difference between the arrival time of the diffraction wave at the breakpoint of upper and lower coal seam is significant,which is easy to separate and extract,and the polarization dip angle of the diffraction wave at the breakpoint of lower coal seam has strong directivity.(2)This paper reveals the polarization characteristics of seismic wave of advanced fault under the coupling effect of coal roadway cavity and loose circle of roadway surrounding rock in full space.Due to the coupling effect of coal roadway cavity and loose circle of roadway surrounding rock,the surface wave in roadway develops,the polarization azimuth of the breakpoint diffraction wave deviates greatly from the theoretical value,while the polarization dip deviates slightly from the theoretical value.When the breakpoint diffracted wave passes through the coal seam,the polarization parameters change and can not be imaged by polarization parameters.When the breakpoint diffraction wave reaches the geophone directly,the polarization parameters are accurate,and the breakpoint can be accurately imaged by polarization parameters.(3)A new Hilbert polarization imaging method for high precision positioning of the faulted coal seam in front of the tunneling face is proposed.Convergence imaging of the faulted seam is carried out through this method,which using Hilbert polarization to analyze polarization parameters of the break point diffracted wave,calculating the possible diffraction points through geophone combination and taking the spatial density distribution as the criterion.Hilbert polarization imaging method proposed in this paper does not need to consider the velocity modeling problem,and the accurate location of the faulted coal seam can be achieved by using polarization characteristics of time-domain diffracted wave.(4)The advanced quantitative detection of coal roadway faults in typical mining areas has been realized.HTPs Filter mine roadway multi-wave and multi-component seismic data processing system based on Visual C++.net platform was developed.Field tests were carried out in typical mining areas,and advanced fault detection model was constructed.The empirical results show that Hilbert polarization imaging technology can provide necessary technical parameters for safe tunneling of coal roadway.