Construction of Grout-Plugs within Karstic Collapse Columns to Restore Flooded Mines: A Case Study at Dongpang Mine, Xingtai, China

Dongpang Mine, located in Xingtai, China, was flooded in 2003 by a water inrush in which pressurized groundwater in the underlying limestone suddenly flowed into the mine through a karstic collapse column. In order to restore the flooded mine and prevent future water inrushes, a grout-plug was constructed within the collapse feature. The grouting was conducted on the surface by drilling boreholes and pumping grout into the collapse column, while monitoring of the effectiveness of the plug was carried out underground by artesian flow tests through directionally drilled wells. The completed grout-plug is 73m high. Construction of such a large in-situ plug in an underground collapse feature overcame several engineering challenges. A key component to the success of this project was that all the grout holes including primary, secondary and tertiary ones were directed precisely to the designed locations. In addition, the technique, quality control, grouting stages, and completion criteria of each stage were tailored to the site-specific conditions. The effectiveness of completed plug was evaluated by core samples collected at boreholes and underground water-injection and water drainage tests.