I am in the planning stage of a more complicated project.
I am looking for experiences (positive, but negative may be useful too!) with horizontal drilling in clay under a slab.
Core drilling through the foundation is not the issue, consider it done.
I am looking for recommendation for:
(1) which motorized mechanical drill to use (or experiences with hand coring/drilling tools) and
(2) what core/drill/auger tip to use and
(3) whether extension pieces exist to drill up to 16 feet distance
(4) Finally, I need an idea how accurate it is to bore with a recommended tool/method (depends of course on rock density).
All of this from a manhole while reaching through a cored foundation wall, or deep enough to go under a footer. I imagine any motorized tool would have to be able to be anchored against the foundation wall.
Also not unimportant: assume all pipe obstructions are exactly known under the slab.
I have found tools on line but am looking for specific experiences of people in our industry.
Leo Moorman
Radon Home Measurement and Mitigation, Inc.
Check out customaugers.com . I've never gone 16 ft, but I'm pretty confident I could based on my experience with those augers. A 4.75" bit will go through the hardest clay I've seen with a standard right angle drill. Good luck, sounds like an interesting project!
I have seen this setup used to install soil gas monitoring points in the past. You can rent these kits as well as buy them. They were drilling to 12' in a soft silty sand and the large rotohammer was giving them a real work out. 12' is a really long way to drill, especially in clay. The power required to turn the mass of the drill bit itself becomes significant. I have had professional drillers try to talk me out of going 12' in clay with a portable 420M Geoprobe.. I would prefer an extraction trench if possible.
I have heard of a project where the drilling was done with a post-hole drilling machine, with bits made of threaded pipe sections with 1/4" rebar tack welded around them in a spiral. Don't want to mention names on public forum without permission, but can email you.