Vertical prefabricated drains, or wick drains as they are also called, are used to accelerate the consolidation of soft, low permeability soils. They are closely related to the consolidation phenomenon.
Why is it used?
Prefabricated Vertical Drain (PVD) is made of corrugated plastic core covered with geotextile. The width is typically 100 mm and the thickness is ranging from 3 to 5 mm. The installation of PVD is done through a specially constructed mast with a steel mandrel installed on an excavator to push the PVD to the required depth on a grid pattern.
How does it work?
PVD increases the apparent mass permeability of the soft soils and thus reduces the consolidation time. It is used in combination with temporary preload fill to expedite full or partial primary consolidation as well as induce several decades of secondary consolidation (creep) settlement.
The main geotechnical parameters (settlements, pore water pressure, horizontal displacements) are monitored via appropriate instruments throughout the consolidation period to validate the design and ensure safe phasing for the construction of the embankment.
For projects that can allow time for staged construction ranging from 6 to 12 months, the vertical drain technology can be very efficient and economic. The most common application is the linear infrastructure such as road or rail embankments. It has also been used for land reclamation over soft soils for the construction of airport runways and taxiways, marine terminals or other structures where the load intensity is not too high.