Vertical Drain VD
Vertical Drain technology is closely related to the consolidation* phenomenon. Often applied with the preload fill is one of the most reliable and certainly the most economical ground improvement method.
*)The consolidation is a soil compression process under its own or external load. The consolidation mechanism is based on the reduction of the pore space (so also the volume of the soil) combined with the squeezing out the water from the granular soil structure. Consolidation affects different mineral soils (particularly important for clays and other cohesive soils) and organic soils (eg. peat, gyttia and other).
Vertical drain technology consists of installing prefabricated drains in the ground, which accelerate the consolidation of impervious soils. Vertical drains are flat, plastic, flexible cables with round or oval cross–section, which, when installed in a suitable spacing, dozens of times increase the permeability of the soil. In order to accelerate the consolidation, together with vertical drainage temporary load embankment is used. Vertical drainage is most commonly used in cohesive soils under road embankments or parking lots.
For projects that can allow time for staged construction, the vertical drain technology can be very efficient and economic. The most common application of this technology is the linear infrastructure such as road or rail embankments. VD technology is also used in tandem with other Menard technologies, for example: Menard Vacuum Consolidation or Dynamic Compaction. Drains treat the soil, greatly accelerating the time of consolidation. The method of vertical drainage is often the only alternative to the implementation of indirect foundation on stilts, especially when in the substrate present are organic soils with high moisture content and thickness in excess of several meters. Drains can reach up to 50m. VD technology can be successfully applied not only to organic soils (peats, aggregate muds, gyttjas), but also to soft cohesive soils (clay).
Depending on the geological conditions and design requirements, the drains spacing is assumed to be from 0.5m to 1.5m. Maximum loads transferred to the consolidated soil (after its draining) depend directly on the type, degree of the consolidation, the nature of the structure and permissible subsidence levels.