Drains are formed by a filter lining that is driven into the ground, protected on the outside by a needle or metal cover in a rhomboid or rectangular shape, which is removed once the drain has been driven in. A special piece of equipment is used for this which, using a hydraulic capstan or some other system, makes the needle and lining move up or down on a vertical path.
The purpose of the drains is to reduce the flow path of the pore water in the consolidation process, speeding up its expulsion towards the surface, and increasing the rate of settlement.
Preloading with or without wick drains allows settlement to occur before the construction begins on the planned structure, so once it is actually built, any further settlement will be insignificant.
This technique is also applicable off-shore to increase the rate of settlement on the sea bed, for which special rigs are used, installed on pontoons.
GEOCISA has equipment that can install wick drains down to a depth of 30 m.