limestone leak slide

25MGD Sinkhole Leak Grouting

Roanoke, Virginia

limestone leak featured

The Job

An underground minerals mine started to lose up to 8VF per day of mine due to water infiltration. Investigation of an adjacent stream uncovered multiple sinkholes which had opened up where the stream crossed a fault. Two sinkholes were adjacent to bridge abutments of a public road, which served as the sole access for multiple homes and farms.

The Challenge

Mine personnel started to self-perform chemical grout in some of the sinkholes. Due to the slow rate of grout installation relative to the water flow, the self-performed grouting was unsuccessful.

Due to endangered fish habitats within the stream, cementitious grouts weren’t allowed, and any chemical grouts needed to be certified for potable water use.

The Solution

CJGeo mobilized two polyurethane grouting crews in the third week of the Covid-19 pandemic to the site. To facilitate safe access to the site, all grouting was performed from aerial platforms reaching out over the work area.

During the grouting process, multiple additional sinkholes opened up; CJGeo would seal one sinkhole, and an adjacent soil filled feature would blow out. Super sacs of aggregate were dropped in the sinkhole throats to fill the bulk of voids, and then polyurethane grouting was performed below the super sacs.

Using nearly 50,000 pounds of CJGrout 35NHV61, CJGeo was able to slow the leaks to the point where no additional sinkholes formed, and the mine’s pumps were able to dewater the facility.

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