| Application | Anchors |
|---|---|
| Location | Stirlingshire, Scotland |
| Hammer | Numa RC100 |
| Bit | Reverse Circulation |
| Hole Size | 12-1/4” (311 mm) |
| Depth or Length | 118 – 184 feet (36 to 56 metres) |
| Formation | Concrete, Schist Bedrock with Quartz Veins |
| Rig Type | Hutte KBR 203 |
Description
After 100 years of service, a Scottish dam was in need of strengthening by the installation of a line of high capacity ground anchors to post-tension the structure. A Hutte KBR 203 drilling rig with a Numa Reverse Circulation RC100 down-the-hole (DTH) hammer was used to drill 12-1/4” (311mm) diameter anchor holes into schist with quartz veins bedrock. Numa Reverse Circulation (RC) products were chosen due to their ability to bring all cuttings up the center of the hammer and drill string to be safely collected at the surface. Ejecting cuttings up the center collection tube reduces hole cleaning problems and helps in formations where risk of hole collapse is high.
To ensure high levels of environmental control, reverse circulation flush was used, with the disposal of the cuttings and water arisings handled by the main contractor through a complex system of dewatering, skips and tankers. As the work progressed towards the area of deepest bedrock, water entering the drill holes increased. Holes progressed between 36 to 82 feet (11 and 25 metres) into rock, giving overall hole depths between 118 to 184 feet (36 – 56 metres). The drilling proved to be a challenge but the Numa RC100 was able to successfully conquer the conditions and provide the right outcome for the project.