Horizontal Directional Drilling (HDD) is a trenchless construction
technique, which uses guided drilling for creating an arc profile. This
technique is used for long distances such as under rivers, lagoons, or
highly urbanized areas.
Drilling process
The process involves three main stages: drilling of a pilot hole,
pilot hole enlargement, and pullback installation of the carrier pipe.
The technique can be used in soft soils.The bore hole is supported by a
bentonite drilling fluid, which avoids collapsing of the hole.
Advantages
HDD offers several advantages when compared to other trenchless
construction methods:
Complicated
crossings can be quickly and economically accomplished with a great
degree of accuracy since it is possible to monitor and control the
drilling operation.
Sufficient depth can
be accomplished to avoid other utilities.
In river crossing
applications, danger of river bed erosion and possible damage from
river traffic is eliminated.
