Comprehensive investigation of water-conducting channels in near-sea limestone mines using microtremor survey, electrical resistivity tomography, and tracer tests: a case study in Beihai City, China

This study aims to identify distribution position of water-conducting channels in the mining area and provide a reliable guide for the design of grouting curtains in mines. A comprehensive exploration method for water-conducting channels in limestone mines was proposed in combination with surface and cross-hole electrical resistivity tomography, microtremor survey method, and tracer tests. First, the microtremor survey method and surface electrical resistivity tomography were used for combined depth and shallow detection; three shear wave velocity profiles and four resistivity profiles were obtained to delineate the main distribution areas of water-conducting channels. Next, six boreholes were drilled in these areas to verify the microtremor survey method and surface electrical resistivity tomography detection results. The higher-precision cross-hole electrical resistivity tomography was performed at boreholes to determine the geometry and depth of water-conducting channels. Finally, combined with the corresponding geological survey and analysis, the tracer tests were carried out at three boreholes. The path distribution of the water-conducting channels was inferred by analysing the hydraulic connection with main water-gushing points of the mine. Furthermore, the detection results were comprehensively explained and the influence of mining on karst was discussed. The results indicate that the combination of microtremor survey, electrical resistivity tomography, and tracer tests can ascertain spatial distribution of water-conducting channels, which could provide a basis for the design and parameter selection of subsequent water-conducting channels grouting treatment programmes.