CommScope ConQuest Conduit Construction - Manual (Page 25)

Underground Installation Methods 4.7
HDD - Horizontal Directional Boring
Directional Bores *
Directional boring is accomplished by using a steerable drill
stem. The equipment operator can control the depth and direction
of the boring. Very long bore lengths can be accomplished by
using directional boring devices.
Subsurface crossings are generally accomplished by digging a
trench on each side of the crossing to allow guiding and retrieval
of the drill stem. The construction equipment manufacturer
specifies detailed equipment operation and excavation procedures.
Generally, a bore should be kept as straight as possible. The hole may be enlarged using reamers. The reamer should
be at least 1.5x - 2x larger in diameter than the conduit being installed. A larger ‘outer’ conduit should be installed at
strategic locations (i.e. street crossings) for use as a sleeve for smaller conduit.
After the bore is complete, attach the conduit to the drill stem with the appropriate grip and swivel. Pull the drill stem/
back reamer and conduit through the bore. Longer pulls will require tension monitoring. The back reamer size will be
determined by the size and number of conduits being pulled.
General Process
- Set up equipment according to manufacturer’s recommendations and good practices
- Do an pre-construction walkover and inspection
- Prior to drilling, mix drilling fluid and quantity required
- Excavate surface entry pit to contain drill fluid and allow for drill stem angle entry
- Use correct drill bit for ground conditions
CommScope Best Practice Recommendations
- Best practice - use reamer 2x larger than the pipe outer diameter.
-
Drilling Fluid - the correct fluid quantity must be mixed prior to drilling.
An incorrect mix could result in high friction and fluid loss in the soil.
Long pulls require a correct mix and quantity to reduce friction on the pipe.
*Source Cited: ‘Horizontal Directional Drilling - Good Practices and Guidelines’
published by HDD Consortium/NASTT.