Advances of mine electrical resistivity method applied in coal seam mining destruction and water inrush monitoring

Coal seam mining destruction might cause water inrush which threatens the safety of mine production seriously.Prevention of coal mine water inrush is mainly focused on detection of hidden dangerous geological structures before mining.Effective detection approach for water channel,which develops dynamically during mining process,is still insufficient.This paper starts from analysis of the mechanism of water inrush from roof and floor of coal mine,compares different monitoring methods used in coal mine,such as multi-parameter sensor monitoring,micro-seismic monitoring and electrical resistivity monitoring.Among those methods,electrical resistivity monitoring is widely used in coal seam mining destruction and water inrush monitoring,because of its sensitivity to resistivity changes of coal and rock mass.Mine electrical resistivity monitoring was mainly used to monitor the destruction of coal seam roof and floor at first.With the successful development of mine electrical resistivity monitoring equipment,relevant scholars have carried out in-depth research on the electric field response characteristics of mining failure process.Mine electrical monitoring gradually develops towards water hazard monitoring,and different observation methods have been developed in underground field application.Apparent resistivity profile or resistivity inversion imaging are commonly used in processing and interpretation of mine electrical resistivity monitoring data.However,the imaging resolution is low because of various interference factors in data acquisition.Time-lapse electrical resistivity tomography,which is widely used in near-surface detection,greatly improved the imaging resolution of monitoring data,by improving data acquisition methods,using data preprocessing,optimizing inversion methods and choosing appropriate regularization constraints in inversion process,etc.This method can also be applied to the processing and interpretation of underground electrical resistivity monitoring data in coal mines.Early mine electrical instruments were mainly used for static detection of water hazards in working face.In recent years,the mine electrical resistivity monitoring equipment has been developed successfully and has entered the stage of popularization and application.With the implementation of the new edition of “Detailed Rules for Coal Mine Water Prevention and Control”(2018),new opportunity for mine electrical resistivity monitoring is coming.However,the underground environment of coal mine is complex and the observation space is limited.There are still many problems to be solved when mine electrical resistivity method is used to monitor coal seam mining destruction and water inrush,such as electromagnetic noise,consistency correction,imaging method,multi-solutions,early warning of water inrush,and so on.To solve these problems,it is necessary to further enhance the anti-interference ability of monitoring equipment,improve data preprocessing method,use time-lapse electrical resistivity tomography to increase interpretation accuracy,and carry out more research on electric field response characteristics of development process of water channel and qualitative relationship between electrical change and risk of water inrush.Finally,the purpose of monitoring and early warning of mine water inrush could be achieved.