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Void Filling – Borehole Seals

Void Filling – Borehole Seals

The Issue

Old mine workings were preventing the deployment of heavy equipment to repair a pipeline which had been installed above the workings. Attempts had been made to fill the workings with grout, however on closer inspection it was found that the grout had run off down three hitherto unknown drifts. The entrances required blocking in order to support the filling of the workings.

The Solution

Boreholes had been drilled down to the entrance of each drifts, between 13m and 20m below the surface, with additional holes drilled for monitoring the progress, all were cased. A mixing tube was added to the top of borehole seals to enable the material to be mixed at that point, thereby reducing the chance of lines being blocked by product curing. Using the drilling logs for reference, the borehole seals were lowered down the holes to the correct depth with material lines attached.

With the seal burst pressure set to 20 bar, MasterRoc MP367 PUS was then pumped down through the borehole seals using a Desoi L36 pump to form a barrier.

The Result

The results were captured using a camera lowered down an adjacent borehole. Approximately 14 Tonne of material was used to successfully block the drifts, which enabled the successful grouting of the workings and subsequent repair of the pipeline