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.

Equipment used