jetting

(civil engineering) A method of driving piles or well points into sand by using a jet of water to break the soil.
(engineering) During molding of plastics, the turbulent flow of molten resin from an undersized gate or thin section into a thicker mold section, as opposed to laminar, progressive flow.

1. The sinking of piles or well points by the use of a water jet, e.g., through a hole in a cast concrete pole or by inserting a pile in a hole produced by jetting; esp. used where pile driving may damage neighboring buildings.
2. The compacting of backfill around a pipe by introducing water under pressure in the trench in which the pipe is laid.