Research And Application Of Inequality-constrained Resistivity Three-dimensional Tomography Technology In Goaf Detectio

Coal still plays an important role in China’s energy structure.After the coal is mined,it has a major safety hazard to people’s economic property and life safety.Due to the thin thickness of the coal mine,the large thickness of coal seam mining and the buried coal seam,the goaf has great influence on the ground,and the surface deformation is severe.To seek a technical method that can determine the horizontal occurrence range and vertical buried depth of the goaf in the northern Shaanxi mining area.At present,the main detection method of goaf is twodimensional detection,which is unable to realize the study of three-dimensional spatial distribution of goaf.In this paper,the resistivity 3 D tomography technique is studied in the selected area,in order to provide a reliable method for the distribution of 3 D,open up ideas for the study of goaf,and expand the application range of 3 D electrical method.On the analysis of the data and the formation mechanism of goaf.On this basis,the corresponding model combining the actual geological conditions of work area,using Res2 DMOD,Res3DMOD,Res2 DINV,Res3DINV software,numerical simulation study,optimizing the actual data acquisition device,data acquisition and inversion method,it is concluded that a suitable for the study of 3 d spatial distribution in northern shaanxi mining area.Finally,the technical method is applied in engineering,and compares the results with the results of the transfer hole data,so as to verify the correctness and practicability of the method.The study concluded the following conclusion:(1)The forward accuracy of finite unit method is slightly higher and finite difference method,both of which are higher than the analytical method.Compared with the finite difference method,finite unit method and the degree of the anomaly,there are some differences in the anomalous value,with a difference of about3%～5%.Finite difference method is slightly less than the finite unit method,the error within 0.8%,the calculation error is small,strong convergence,into the inversion,early finite unit inversion square error is faster,the final value is slightly smaller than finite difference method,about 0～0.01%,small difference,finite unit method for slightly higher accuracy.(2)The detection depth of the secondary device is deeper than that of the temperature temperature device and the tripole device,and the data collected is complete,which is more suitable for 3 D detection in the goaf.Because the detection depth depends on the distance of the power supply electrodes,the dipole and tripole devices with infinite electrodes are deeply detected,and the deepest,and the data collection is more comprehensive.(3)The cross-form data collection method is less and less time-consuming,but the inversion effect is slightly poor.The whole data collection method is large and time-consuming,and the inversion effect is slightly better.The two data collection methods basically reflect the main characteristics of the model,and the whole data collection method is better in terms of the effect of details.(4)The inversion effect of the inequality constraint least squares method is better than the traditional least squares method.The former has a shorter inversion time,smaller mean square error,less number of iterations,and the anomaly value is closer to the model setting value,the inversion effect is better,and the overall reflection is closer to the model setting.(5)The calculation of the water content of the goaf and its distribution range and morphology by the inversion results of three-position tomography are consistent with the drilling data,indicating that the resistivity 3 D chromatography with inequality constraint can be effectively applied in the study of goaf detection.This research opens up the research idea of goaf,expands the application scope of 3 d electric method,and provides the idea and reference to guide similar practical engineering through data simulation.