RESEARCH AND APPLICATION OF FULL-SPACE TRANSIENT ELECTROMAGNETIC RESPONSE IN CONCEALED WATER SOURCE ENVIRONMENT AFFECTED BY LOW RESISTIVITY SHIELDING

The massive mining of coal mines brings seriously damage to the water resources, resulting in groundwater's loss and leakage, and surface water's decline and pollution. Therefore, great significance should be attached to the prediction and prevention of water disaster in the mine production process. Endowed with sensitivity to low resistance, high accuracy in detection and efficiency in construction, transient electromagnetic method is widely used to detect abnormal water-bearing bodies in coal and rock mass. However, its sensitivity gives rise to the shielding effect of low resistivity layer, affecting its detection accuracy in return. By establishing a three-dimensional numerical model of low resistance shield above the abnormal water-bearing body in full-space, this paper researches and summarizes the characteristics and rules of electromagnetic field response. Finally, the rules in numerical simulation are verified in the actual field detection situation. Results show that low resistivity shielding will not only affect the response of the abnormal water-bearing bodies to the transient electromagnetic field, but also slow the secondary field transmission and prolong the diffusion time. Therefore, in the application of mine transient electromagnetic, detour should be made around the low resistance body or rock layer near the roadway. When the low resistivity shielding effect cannot be avoided, the observation time should be extended to ensure the observed data are more accurate.