DTH Drilling - guide
How does it work?
DTH drilling uses a mini air or water driven hammer at the end of the drill string. With DTH hammer you can drive down casings or drill rock holes. A rotation unit is part of the drill rig. Air or water are introduced through the drill casing to the drill hammer to drive the piston that strikes the drill bit into the material.
Why DTH drilling?
DTH drilling has the advantage that the force of the percussion, the active strike on the material, hits directly on the drill bit. Which prevents energy loss through a long drill string. This enables efficient drilling regardless of depth. Which we usually describe saying the hammer doesn’t know how deep it is drilling. Using DTH drilling, you can drill a hole several kilometers down.
Water powered drilling
Water drilling, or Wassara is unlike regular drilling with air, but can be used for sensitive ground conditions. Water – as opposed to air – is incompressable and therefore cannot expand underground while you’re drilling. Water powered drill hammers are therefore used to avoid possible damage to adjacent structures, or creating settlement.
Currently a ring or wing system is most commonly used to drive piles or casing. Asymmetrical systems like Tubex or Odex are still used, but not as commonly as previously.
In addition to the drilling rig, you will need a compressor, or a pump for water powered drilling. Air or water hose between the compressor or pump and the rig. Drill pipes that is spliced as you drill down. A Down the hole hammer which apon you attach a pilot bit with carbide button bits. The same equipment is used for driving casing, except you use a pilot bit that fits onto a ring set that is welded to the bottom of the casing. You then drill to you design depth by joining casing and piles as you go. Then you reverse the pilot bit out of the ring bit set a retract the drill string.
As in every drilling project, efficiency depends the operator’s skill, and using the right drilling equipment, and drilling outfit suitable for the specific conditions at the site.
Geomek – Drilling education
Do you want to learn more?
Since several years Geomek holds courses in foundation drilling. The course turns to management and workers at foundation companies, as well as designers.
Focus are on the principles of foundation drilling and maintenance of drilling equipment. Our experience is that there are a lot of money and headache to spear by optimizing drilling and taking care of the gear.