Study On Time-Lapse Electrical Resistivity Tomography Technology For Dynamic Monitoring Of Floor Water Inundation In Coal Mine

Time-lapse electrical restivity tomography technology is a geophysical dynamic monitoring technology.After setting a number of electrodes in the same place,the method takes the appropriate time interval to collect the 2D/3D profile data,and monitors the change of the apparent resistivity of the underground medium in real time.The technology has many advantages,such as multi-channel fast acquisition,quick construction,visual image and high resolution.In this paper,the finite element method is used to simulate the typical floor water inrush anomalies,such as the activation water,the collapse column,the multiple low resistance anomaly,the dynamic change of the floor rock failure and the pressure rise of the coal seam floor,respectively,and the response characteristics of the geoelectric anomaly body under different water inrush conditions of the coal mine floor are studied.The forward results show that the response of the geoanomaly body is obvious,indicating that the time-lapse electrical restivity tomography technology can be applied to the dynamic monitoring of water inrush in the coal floor.Through the analysis of the positive and negative variation characteristics of the difference of the apparent resistivity,it is possible to deduce the water rich change of the fractured rock mass,pay attention to the region with severe change,and make the prediction and early warning of water inrush in time to avoid the occurrence of the malignant accident.In order to meet the needs of real-time interpretation of the dynamic monitoring of water inrush for coal mine floor,the fast imaging algorithm of time-lapse resistivity is developed on the basis of "ELRIS2D" open source code,and the result of the last time inversion is used as a priori model of the next time monitoring data inversion,and the calculation speed is improved.Taking the theoretical resistivity data of typical geoelectric models as an example,the inversion results are in good agreement with the actual geoelectric models.In view of the problem that the abnormal boundary of the resistivity image is fuzzy,the abnormal delineation is susceptible to human factors and the difference between positive and negative variation regions of the resistivity difference at different time,distributed fuzzy clustering algorithm is used to analyze the inversion results and the difference data of resistivity,and the centroid position is determined according to the peak value of the probability density curve.The automatic delineation of anomaly and the difference of positive and negative regions of resistivity difference are realized automatically.