Mini-Horizontal Directional Drilling Mean?
Mini-horizontal directional drilling (mini-HDD) is a method for the installation of pipes, conduits and cables using a surface-launched drilling rig. A pilot bore is drilled using a rotating drill string and is then enlarged by a back reamer to the size required for the product pipe. The process utilizes a surface based rig with a steerable drill head. The term mini is used to differentiate between pipes that are too small for man entry.
Mini-horizontal directional drilling is also referred to as guided boring.
Trenchlesspedia Explains Mini-Horizontal Directional Drilling
The maneuverability of this method is facilitated by a slanted drill head, drill heads that are asymmetrical or movable fluid jets at the head. After the initial boring, the hole is expanded through use of a reamer to gradually enlarge the hole to allow installation of the product pipe. During drilling, the bit is laser guided allowing high accuracy- often within 1 inch tolerances. Using mini horizontal directional drilling is costly due to its use of highly specialized equipment and personnel.