To prevent later problems of excess settlement, it is important that excess pore pressures be removed from soft foundation soils within a short time frame. This ensures that foundation shear strength is increased quickly to support embankment and fill loadings. However, soft compressible foundation soils have a low hydraulic conductivity and it takes a long time for excess pore pressures to dissipate and the soil to consolidate. To reduce consolidation time, TenCate Polyfelt® Alidrain prefabricated vertical drains (PVD) are installed to provide a shorter and easier drainage path for the pore water to drain. This speeds up consolidation and the soft foundation gains in shear strength quickly.
TenCate Polyfelt® Alidrain PVD comprises a synthetic drainage core wrapped with a durable fabric of excellent filtration properties. The vertical drain is designed to allow free flow of water in all directions and to ensure the integrity of the drainage system when subjected to tensile, compressive and buckling forces as the soft soil deforms and consolidates.
Once the vertical drains have been installed, fill is placed over the top of the site in order to generate excess pore pressures in the soft foundation soil. The excess pore pressure enables the pore water to drain out of the foundation soil and up the PVD where it is dissipated into a surface drainage blanket, beneath the placed fill. Once the desired consolidation has been achieved, construction continues. A site can be completed in a number of months rather than a number of years if PVDs are not used.
During the consolidation process, lateral soil displacements can cause drains to elongate while vertical soil compression may cause drains to fold and buckle. Drain performance under both conditions must be considered when selecting a PVD as drain failure can jeopardize the construction schedule of the project and the stability of any structures built above it. The complete range of TenCate Polyfelt® Alidrain PVD has been specifically designed to ensure that adequate drainage capability is maintained at all times, even under the most severe soil conditions.
TenCate has the capability to supply large quantities of TenCate Polyfelt® Alidrain PVD to fast-paced projects that require the delivery of the drains within a tight schedule. Its track record in high profile projects is a testament of its reliability to supply high quality and cost effective PVDs for soft soil consolidation projects.
Products Used in Soft Soil Consolidation