Integrated survey approach combining electrical methods and sluicing test for the karst channel in coastal limestone mines: a case study in Beihai, China

The investigation of karst channels is an important work to ensure the safety of underground construction and mining engineering. At present, the combination of the geophysical method and drilling method is the primary and most commonly used approach in karst detection work. However, sometimes limited by conditions, it is difficult to carry out drilling work. In coastal limestone mines, karst is usually developed, so it is crucial and significant to carry out the exploration work on karst channels. Taking a coastal limestone mine in Guangxi Zhuang Autonomous Region of China as a case study, electrical resistivity tomography (ERT) and transient electromagnetic method (TEM) were adopted to investigate the subsurface low-resistivity anomalies. According to the results, the distribution area of karst channels was preliminarily determined by the low-resistivity responses. Then, a sluicing test was carried out to analyze the primary direction of underground karst channels in this area, and several main leakage and outflow points were identified, which could serve as evidence for the channel paths. Besides, the ERT method was used for repeated exploration in the detection area not submerged by seawater after the sluicing test, and the results showed that the low-resistivity responses were consistent before and after the sluicing test. Combining the results of the electrical exploration and the sluicing test, the direction and main pathway of underground runoff were determined, and the distribution of underground karst channels in the study area could be obtained.