Abstract:
Down-The-Hole (DTH) drilling usually uses compressed air to power the hammer. However, there are now DTH hammers on the market which instead of compressed air uses high pressure water to power the hammer. There are several benefits with using water DTH compared to air DTH, which are discussed in more detail in this paper. From a physics point of view many of the benefits arise from the fact that water is an incompressible media and air is not. Energy consumption is roughly a quarter compared to air, resulting in lower carbon emission and a lower energy bill. It is expensive to make compressed air. In the case of water DTH the water leaving the drill bit in the hole is at a low velocity and ambient pressure. However, with air DTH the air leaving the drill bit in the hole is at a high velocity and high pressure. This means that the risk of damaging surrounding structures in sensitive areas such as urban environments and dams, is greatly reduced with water DTH. Straight long holes, no oil pollution of the ground and the ability to maintain performance when drilling in water rich ground are other benefits with water DTH.
One particularly interesting technology in ground engineering is jet-grouting which can be combined with water DTH technology to improve productivity under difficult ground conditions such the presence of hard layers and boulders. The jet-grouting can be done either with a monitor directly above the water hammer or to use an integrated monitor and water DTH hammer, a jet-grouting hammer.
Abstract: Theme 1