Division of foundations
Depending on the depth of the foundation, in the manner of execution and operation of the foundation structure, there are shallow and deep foundations.
Shallow foundations rest directly on the ground, and that's it: foundation footings, feet, grates, plates and crates. This method of foundation is used then, when the load-bearing soil lies at a shallow depth. When there is a load-bearing soil at great depths, i.e.. more than 5,0-7,0 m below the foundation (basement flooring), foundations on piles are used, poles and wells.
Depending on the material used, stone foundations are distinguished, bricks, concrete and reinforced concrete.
The depth of the building foundation depends on the way the underground part is used (condition of use), the depth of the bearing layer appropriate for the structure, taking into account the location of the groundwater level, ground displacement (the height of the anti-displacement soil layer), ground freezing, washing foundations and slope. Grunt, on which the load from the foundation is subject to deformation, which in turn influences the behavior of the building structure.
Relevant soil properties, limiting the specific pressure on them, are * -compressibility and shear strength. Soil compressibility affects the value of the so-called. subsidence, which for various reasons is limited. Exceeding the shear strength of the soil causes a slip surface in the soil and displacement of the soil from under the foundation, which may result in large and rapid displacement of the structure.
According to PN-81 / B-03020 the depth of foundation due to soil freezing is assumed within the limits 80-120 cm. Foundations inside the building, where the ground is protected against freezing, can be placed higher on condition, that the ground will also be protected against freezing during the construction period.