What they are:
Prefabricated Vertical Drains (PVD), also called Wick Drains, are prefabricated drain strips consisting of a polypropylene core extruded into a configuration to transmit a maximum water flow on both sides of the core. The core is wrapped in a non-woven filter, ultrasonically welded together at at the edges. Ground improvement using PVD is applied in areas with compressible water saturated soils such as peat, clay and silty clays, where significant settlements may occur. In addition, increased pore pressure may cause instability of the soil which can result in slip plane failures.
Since water is effectively incompressible, soils must be drained in order for the soil skeleton to support the weight of a new loading condition such as a road embankment, a hydraulic fill or a dike. The prefabricated vertical drains are installed vertically into soft soils in order to shorten the path water must travel, thus accelerating the consolidation. By shortening the drainage path by means of PVD in finesoils, such as silts and clays, it only takes weeks or months instead of years, for the water to escape and the soil to realign into a configuration capable of supporting the new loads. The advantage of using CeTeau-Drain is the reduced construction time and the elimination of the risk of slip plane failure due to maximum efficiency in discharging pore water, whereby the filter jacket provides the optimum filtration and permeability.
What they Do:
Vertical drains are mostly used to shorten the settlement period and thus reduce the construction period of a project, and to avoid post-construction differential settlements. By applying a temporary preload on top of the embankment or fill, the consolidation period can be reduced even more. On top of that, a part of the secondary settlement is also eliminated. Especially for peat soils, an extra preload can be very effective.