## 3 Result and Discussion  
This method can show the location of the low-resistivity body in the model, but the location of the low-resistivity area changes with the depth of the low-resistivity body. The low-resistivity anomaly area is the same as that in the model at a depth of 1.6 m. Moreover, the closer to the surface, the farther the position of the anomalous body extends in the negative Y direction. With the change in depth, the position of the low-resistance anomalous body hardly changes. Therefore, this method can accurately identify low-resistance bodies and can be used in field exploration. Before grouting, data are acquired by laying electrodes and cables on both sides of the roadway. After data acquisition, first, the mutation points of resistivity are eliminated, and the resistivity curve is smoothed. Then, the preprocessed data are converted to the 3D inversion structure, and the data are inverted using RES3D commercial software. The Gaussian Newton method (The Newton-Gauss method consists of linearizing the model equation using a Taylor series expansion around a set of initial parameter values b0, also called preliminary estimates, whereby only the first-order partial derivatives are considered the linear theory is applicable to this linearized model) is used to invert the data. The data with large root mean square (RMS) errors are eliminated by observing inversion results after several inversions, and the data are then inverted once more to decrease the RMS error and promote the precision of continuous inversion. After inversions, the 3D resistivity data volume of the floor of the 8826 working face is obtained. According to the hydrogeological conditions of the working face, \(-\)36.1 m in the floor is the position of the NO.5 LS aquifer. The horizontal resistivity profile of the NO.5 LS aquifer is drawn by 3D Slicer Dicer visualization software. The anomalous resistivity areas of the NO.5 LS aquifers are mainly situated in the ranges of 100 m-150 m and 200 m-240 m in the air return tunnel and 100 m-140 m in the transportation roadway (Figure 7A). Similarly, the horizontal resistivity map of the OLS aquifer is drawn by using Slicer Dicer software (Figure 7B). The areas with anomalous OLS resistivity are within the ranges of 100-130 m and 200-220 m in the air return tunnel and 100-130 m in the transportation roadway. Taking the exposure of drilling 1 as an example, the coal seam floor is 31.75m away from the NO.5 LS, and the thickness of the NO.5 LS is 4.89 m. The distance from the NO.5 LS to the OLS is 3.61 m, and drilling 1 enters the OLS at 32.8 m.  
A comparative analysis of charts A and B in Figure 7 reveals that the anomalous low-resistance areas between the NO.5 LS aquifer and the OLS aquifer are similar. This indicates that the low-resistance anomalous areas may be caused by a single aquifer or multiple aquifers. To prevent water inrush from the floor, the anomalous area of the floor is verified by drilling. As shown in Figure 7, Drillings 1-4 are designed in the return air roadway and drilling 5 is designed in the transportation roadway. According to the experience of the personnel involved with water prevention and control, when the water inflow of the NO.5 LS aquifer is greater than 5 m\({}^{3}\)/h, the aquifer should be grouted. Otherwise, grouting is not necessary. Table 1 shows that the water inflow from the NO.5 LS aquifer is less than 5 m\({}^{3}\)/h in drillings 1 and 5, and the NO.5 LS aquifer is not grouted. The water inflow from the NO.5 LS aquifer is greater than 5 m\({}^{3}\)/h in drillings 2-4. Therefore, the NO.5 LS aquifer needs to be grouted. The water inflow from the OLS aquifer is greater than 5 m\({}^{3}\)/h; thus, all OLS drillings are grouted. The above situation implies that the NO.5 LS aquifer is not rich in water, the OLS aquifer is rich in water, and the water abundance in the OLS is obviously different. After grouting, 3D ERT is carried out on the floor of the working face again, and the results are shown in Figure 7D.