Principles of Construction Often known as "Colcrete" piling, which is a type of trade name. Usually replaced by diaphragm walling methods. Essentially typical bored piles, or down-the-hold bored piles, are constructed with a spacing such that each pile is virtually touching the nect. These are constructed on a hit-and-miss basis. After a suitable length of these piles are in place (often 9 piles or so) a smaller drilling rig follows on behind placing the "colcrete" piles. A small diameter shaft, often 100 mm or so, is drilled on the external face of the pile wall close to the interection between the two main piles. This excavated pile is fitted with a grout tube and backfilled with gravel. The pile is then grouted and forms a seal between the adjacent piles. This type of pile wall can be constructed with either a standard reinforcement cage or a "H" pile.