Integrated surface-underground detection and interpretation method for multi-layer water-filled goaves in deep coal seam mining

Surface TEM encounters challenges in detecting deep multi-layer water-filled goaves due to low-resistivity shielding and limited detection range, while multi-geophysical combinations face target consistency issues. This study proposes the Integrated Surface-Underground Detection and Interpretation Method (ISUDIM) to address these limitations. The ISUDIM method implements a five-step protocol: 1) Calculating roof and floor failure depths to preliminarily locate goaves, 2) constructing forward models to verify detectability, 3) designing sequential underground-surface survey lines with multi-angle configurations, 4) interpreting multi-method results validated by borehole data, and 5) delineating goaves using verified geophysical thresholds (apparent resistivity and polarization rate) projected onto mine plans. An underground wooden dovetail joint structure multi-angle detection system was developed to mitigate human interference, reducing resistivity anomalies in contact and proximity scenarios through angle-adjustable emission (0–360°), roadway-adaptive rollers, and inclination compensation. Field validation at the Yanzishan Coal Mine demonstrated the ISUDIM method and the detection device's effectiveness, accurately detecting the water content in the goaves of the Jurassic and Carboniferous-Permian Strata via drainage verification. The method resolves ambiguity in full-space TEM detection while enabling static water volume estimation, providing critical data for mine water management.