Fig.1 Field investigation site

Due to the collapse and deformation of the ground caused by years of coal mining, some local houses have suffered varying degrees of damage, seriously affecting the normal life and work of villagers. The goaf area and its affected parts are specially investigated, and the surface influence area is delineated, so as to provide a technical basis for future research on the identification of damage to villagers' houses. Using a sampling frequency of 1.25M, the transmission frequency is 4Hz, the number of superposition is 200, the off-time is 0.1488ms, the emission area is 68m2, and the transmission current is 70A. The L61 line is compared with the V8 large wireframe detection at the same point, and the result graph has certain similarity with V8. Most of the measurement points are in villages, and FCTEM is more anti-interference. The apparent resistivity section of the goaf area shows low resistance, which is more consistent with the actual situation.

Fig.2 Comparison of inversion results