The incorporation of geogrids or geotextiles at the base of embankments constructed over soft, compressible ground. Often used in conjunction with Prefabricated Vertical Drains (PVDs) or band drains, or other forms of ground improvement.
Geogrids/geotextiles provide basal reinforcement to embankments by improving the load bearing capacity of the foundation material, particularly when the structure is built over compressible and water saturated soils (e.g. clay and silty clays) or voids (e.g. mining voids, underground caves). For construction over weak soils, basal reinforcement provides short term stability of the embankment, while horizontal and vertical drains (such as band drains) enable the excess pore water pressure to dissipate and the compressible soil to consolidate and settle.
The incorporation of geogrids or geotextiles at the base of embankments constructed over soft compressible ground also (a)provides restraint to failure mechanisms which involve sliding between the embankment and underlying soil (b) reduces the outward movement of soil beneath the embankment which could lead to overall failure.
Basal reinforcement was used in conjunction with band drains in the construction of a distributor road over embankments for a new housing development at Dering Way near Gravesend, in the Thames Gateway. The band drain and basal reinforcement solution was selected because it was economically advantageous. The accelerated settlement produced by the technique enabled the embankment to be used as main site haulage road during the construction phase.