Blind Stope Survey

The application was to survey a Blind Stope – an underground mined out void with no access. This Stope was collapsing and getting bigger. The mine planned to fill the Blind Stope with waste rocks but they needed to determine how big the stope was. They were planned mine the adjacent Stope worth 10s of millions in gold, but they needed to know the dimensions of this Blind Stope first. The only access into the Blind Stope was a 3” drill hole 110m long and at 11 degree dip. The hole was cased with drill rods that were extremely rusty. There was no technology available because the normally minimum angle is 45 degrees. At 45 degrees or more, a scanner can be lowered using gravity. This is why we brought in the rod and eRodder to assist with pushing the scanner 110m.

The set-up included 200m of 11mm diameter fiberglass rod, an electric rod Pusher (eRodder) and GeoSight GSM scanner. The eRodder pushed the scanner through the hole and at around 50m mark the resistance increased caused by the rust inside the pipe. We tried running salt water down the pipe to provide lubrication. The only water available was 4 times more salty than sea water but did allow the scanner to be pushed a bit easier. The first hole was blocked at 110m mark by a large rock. We returned the next day and tried to push the scanner down another hole that was at a 10degree angle. Again, this was harder to push the scanner through the rusty pipe so we ran 30 litres of vegetable oil down the pipe which made it easier for the eRodder to push the scanner 110m. We finally obtained good results and the mine was able to determine the size and shape of the Blind Stope.