Near⁃source effect of natural electric field responding to mining⁃induced rock mass destruction

In whole⁃space geoelectric field detection，new breakthroughs may be obtained in multiphase media coupling system evolution detection and disaster early warning as long as the temporal advanced sensing abilities of the natural electric field for specific dynamic processes in rock mass(rock mass destruction，groundwater seepage，fluid⁃solid cou⁃ pling evolution，etc.)can be effectively combined with the spatial characterization abilities of direct current resistivi⁃ ty methods and the induced polarization methods，provided that these detection abilities and their mechanisms of the natural electric field are clarified. In this paper，similar material simulation methods in mine rock mechanics field were introduced to overcome the difficulties both of the cross⁃scale research and the coupling analysis of multiple parameters of natural electric field，including self⁃potential，spontaneous potential，surface potential，induction charge， et al. The cause of abnormal response of the natural electric field was discussed as well as the experimental results at three different scales，including rock sample loading experiments(cm level)，physical simulation experiments(m level)，and mine in⁃situ experiments(sub⁃km level). Thus，its connotation and scientific significance were put forward and explained of the near⁃field effect in natural electric field responding to mining⁃induced rock mass destruction. Ad⁃ ditionally，kay problems in further research of natural electric field method(self⁃potential method)for rock mass de⁃ struction detection were pointed out. The experimental results jointly show that the phase，frequency and amplitude of the self⁃potential signal can all be used to characterize mining⁃induced rock mass destruction，and compared with far area，it is different in near area of the fracture source with the distinguishing feature as the higher frequencies，bigger amplitudes and different phases. The greater the self⁃potential amplitudes(even greater in near area)，the more ener⁃ gy the rock mass releases and more seriously it would destruct. With the same amplitude level，the higher the self⁃po⁃ tential frequencies(even higher in near area)，the more frequently the rock mass fractures and more serious it would destruct. The more the points with different self⁃potential phases(in near area would be different while in far ar⁃ ea would be same)，the more fracture points in the rock mass and more seriously it would destruct. The in⁃depth dis⁃ closure of the natural electric field response mechanism to engineering rock mass destruction must be constrained by specific engineering scenarios and depend on the in⁃depth multidisciplinary cross⁃discipline research，improvement of simulation level and testing technology，employment of nonlinear signal analysis methods，etc. The construction of par⁃ allel detection and multi⁃parameter feature fusion of the self⁃potential method，the direct current resistivity methods and the induced polarization methods is expected to provide new geoelectrical theory in order to support the intelli⁃ gence，accurate detection of disaster sources as well as disaster warning.