Development And Signal Analysis Of MEMS Digital Geophone In Coal Mine

With the improvement of physical resolution,fidelity and accuracy of seismic detection,the traditional moving-coil geophone,which has been used for decades,can not meet the demand,and became a major obstacle to geophysics exploration.At present,the moving coil geophone is still used in underground trough wave.Therefore,the modern underground coal seismic exploration system urgently needs a higher performance geophone.Based on the seismic exploration project of underground trough wave in coal mine,the research methods of MEMS accelerometer selection,explosion-proof shell design,surface wave acquisition experiment,underground trough wave acquisition experiment and signal analysis are adopted in this paper,the geophone used in the borehole is successfully developed and its performance is tested and compared.The main results achieved and conclusions drawn are as follows:(1)a MEMS digital geophone is developed in this paper.According to the requirement of explosion-proof for electrical equipment in coal safety regulations,the cylindrical explosion-proof shell with stainless steel flange and 70 mm length and42 mm diameter of steel of enough thickness is adopted.The MEMS digital geophone has a dynamic range of 110 d B,a bandwidth of 1000 Hz,high sensitivity and small volume.The explosion-proof shell can basically meet the construction requirements in the coal mine,and the wiring mode is also easy to connect various types of seismographs,so that it is convenient to be used in seismic exploration projects.(2)Based on the principle of surface wave exploration,a comparison experiment of surface wave acquisition was carried out in the field.It can be seen from the waveforms that the signals of MEMS geophone and moving coil geophone are in good agreement,and the low frequency part has stronger energy and wider frequency band Based on the time-frequency analysis of the generalized s-transform,the dispersion and frequency spectrum of the surface wave are extracted,and the distortion of the surface wave signal collected by the MEMS digital geophone is lower,and the dispersion curve extracted by the high-frequency part is more accurate.Compared with the dynamic loop geophone,the MEMS geophone has the advantages of stronger lowfrequency energy,wider frequency band and clearer dispersion curve,which is suitable for surface wave exploration.(3)according to the principle of trough wave exploration,the contrast experiment of underground trough wave acquisition was carried out in Jinniu mine.Through the analysis of the waveform,frequency spectrum and diffraction migration imaging of the collected trough wave signal,it is concluded that the MEMS acceleration geophone has the advantages of richer high frequency signal and wider frequency band than the slot wave signal collected by the movable coil geophone.The results show that the MEMS accelerometer has the advantages of richer high frequency signal and wider frequency band compared with the slot wave signal collected by the movable coil geophone.Figure [45] Table [3] Reference [102]...