With shallow foundations, care must be taken to ensure that it is embedded in the ground at least below the frost line (in Germany at least 80 cm) . This prevents uplifts and subsidence , and thus cracks, from occurring when the ground freezes .
Different types of shallow foundations
Depending on the application and cost optimization, one of the following flat foundations is used.
Single or point foundation
These are arranged under columns and supports, whereby very large loads can be transferred here.
In the case of precast construction, the precast columns are placed in these cages and then grouted with mortar.
Under walls and loads at short intervals, strip foundations are ideal for introducing loads into the ground.
If the structural loads have to be distributed in order to be introduced evenly into the subsoil, the foundation plate is particularly economical. This also has the advantage that a floor is created on which work can be carried out.
If there is groundwater, it is held back by the side of the tub, whereby attention must also be paid to the tightness of the tub. There are extensive suggestions and guidelines for this.
Difference between shallow and deep foundations in construction practice
In principle, for economic reasons, it should first be examined whether the simpler form of the shallow foundation can be chosen.
A deep foundation is usually only chosen if the stable soil layers are only available at greater depths.
The load-bearing capacity of the shallow foundation can be controlled via the foundation sizes and the embedment depths. These are to be selected in such a way that both the stability is guaranteed and the deformations are compatible.
In the case of stable soil layers at easily accessible depths, soil replacement can also be more economical than deep foundations.
Between shallow and deep foundations, there are also intermediate solutions such as B. Pillar or well foundations. Here, the non-load-bearing ground is excavated or blocked and replaced with unreinforced concrete.
If shoring is necessary, manhole rings are also used for this (well foundation). They are excavated from the inside and at the same time lowered down to stable soil layers. They are then filled with unreinforced concrete.
The best known example of a failed shallow foundation is the Leaning Tower of Pisa .
- DIN 1054: 2010-12 "Subsoil - Proof of safety in earthworks and foundation work - Supplementary regulations to DIN EN 1997-1" , p. 40
- Simple shallow foundations. Lecture notes, chair for foundation engineering, soil mechanics, rock mechanics and tunnel construction; Geotechnical Center, Technical University of Munich, no year. (PDF; 462 kB)