Mining
The San Geronimo mine in Chile was facing the challenge of creating open slots with a high productivity in a safe manner.
San Geronimo, Chile
San Geronimo Mine
W70 & W100 Hammer
There is no other technology that is better than the Wassara DTH hammer when it comes to drilling a long hole rise, due to the fact of the straight holes, high productivity and low stress caused on the host rock.
Opening slots – as real challenge
The San Geronimo underground copper mine, located in Chile, was facing the same challenge as most underground mines – the ability to create open slots with a high productivity in a safe manner. The opening slots are the first holes to blast, creating a void that is used for the production blasting.
Previously, the staff at San Geronimo used the traditional air leg raise miner for the opening slots. A miner worked his way up the hole on ladders and drilled and blasted, cut by cut. This method was not very productive and posed a great hazard for the raise miner.
To create one open slot with the dimension of roughly 1.2 m x 1.2 m and 20 m in length with this method it took roughly 28 days and 3-4 miners were required. In the search for alternative ways of drilling opening slots, the use of a box-hole rig was quickly eliminated due to the high cost and requirement of large development drives.
The Wassara solution
Wassaras water-powered DTH (Down-The-Hole) hammer enables very straight holes with less than 1% deviation in traditional lengths of long hole rises. The successful reference from the LKAB mines in Sweden, where the Wassara hammer is being used for long hole rises up to 35 m in length, made the choice easy for the mine.
The mine made some modifications to a rig (such as a rotation unit and breakout table) in order to utilize the Wassara DTH-hammer.
The drill pattern of the long hole rise consist of 82 mm (3.25”) blast holes and 127 mm (5”) open void holes. The length of the long hole rises varies around 20 m and are 90 degree upwards and have about 70 degree side rotation.
| DTH Hammer | W70 & W100 Hammer |
| Drill bit | Ø 82 mm (3.25”) & Ø 127 mm (5”) |
| Drilling fluid | Clean water |
| Drill rods | 63.5 mm (2½”) & 89 mm (3½”) |
| Rig | Atlas Copco Boomer 281 |
| Water pump | WASP 80 Diesel |
| Borehole length | 20 meters in average |
| Geologic formation | Sandstone and other rock types, with hardness of 135 MPa – 160 MPa |
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