Groundwater Flow Characterization in Karst Area Using Dye Tracer Test

A tracer test using fluorescent dye, uranine, was performed to identify connectivity between sinkhole at the bottom of a small reservoir and a gallery of limestone mine. Tracer solution of 6.5m³ with the concentration of 6.84×10⁴μg/L was injected at a rate of 1.32×10²m³/d for 71 minutes into sinkhole and then concentration breakthroughs were monitored at three seepage points in the gallery. Water inflow rate to the sinkhole, seepage rate from the seepage point 1, 2, and 3 in the gallery were measured to be 2.39×10³, 3.31×10³, 95.2, 24.7m³/d, respectively. The breakthrough curves show that there are connections between sinkhole and three seepage points. Peak concentration at the seepage point 1, 2 and 3 were 707, 707 and 150μg/L and groundwater velocity were 7.11×10³, 5.91×10³ and 3.11×10³m/d, respectively. Tracer recovery rate was calculated to be 73.80, 2.08, 0.22% at seepage point 1, 2 and 3, respectively. It was found from the test that about 76% of inflowing water to the sinkhole flow to the seepage points in the mine gallery and 24% of it flow out to ambient groundwater system and 53% of seepage water to the mine gallery comes from sinkhole and 47% of it comes from ambient groundwater system. It was concluded from the test results that the sinkhole at the bottom of the small reservoir was formed by over excavation of limestone mine gallery and its connectivity is about 76%.

Acknowledgements:  This research was partially supported by the Green Up 30 project of the Korea Institute of Construction and Transportation Technology Evaluation and Planning funded by the Ministry of Land, Transport and Maritime Affairs and by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources(KIGAM) funded by the Ministry of Knowledge and Economy.