Areas of low lying ground near the coast and around rivers close to towns and cities have been raised by tipping waste, refuse and soil from excavations. Over the years the fill will have settled and consolidated to some extent. Areas of made up ground are often used for buildings as the towns and cities expand. Because of the varied nature of the materials tipped to fill and raise ground levels and the uncertainty of the bearing capacity of the fill, conventional foundations may well be unsatisfactory as a foundation.
An example of made up ground is the area of Westminster now known as Pimlico where the soil excavated during the construction of the London docks was transported by barge to what was low lying land that was usually flooded when high tides and heavy rainfall caused the Thames river to overflow. The raised land was subsequently heavily built on.
A uniformly stable, natural, sound foundation may well be some 3 or more metres below the surface of made up ground. To excavate to that level below the surface for conventional strip foundations would be grossly uneconomic. A solution is the use of piers on isolated pad foundations supporting reinforced concrete ground beams on which walls are raised, as illustrated in Fig. 4.
Fig.4 Pad foundation.