Foundation works is the phase that technologically follows after preparatory and earthworks.
FOUNDATIONS are the lowest construction part of the building in direct contact with the ground, and they carry the entire load of the building and transfer it to the foundation soil.
Foundations are designed according to the permissible bearing capacity of the foundation soil (in terms of contact area). The data required for foundation (bearing capacity and depth of the bearing layer) can be found in the Geotechnical report.
The soil bearing capacity can be based on bearing pressure and friction, which changes or increases with foundation depth due to greater compaction and density of the terrain.
Considering the different qualities (bearing capacity) of the foundation soil and varying depths of the bearing layer (sometimes there is no bearing layer at the usable depth) and very different geometrical–construction solutions, there are different methods of foundation:
1. SHALLOW FOUNDATION – carried out on the practical surface of the terrain with minimal excavation (minimum depth 80 cm) because the bearing soil is very shallow relative to the terrain surface, and at the foundation level there is no groundwater and freezing of the bearing layer is avoided. The structure must be such that the loads are acceptable.
Types of shallow foundations:
- STRIP FOUNDATION – long and much larger in length, width, and depth, so they can also be called continuous. These are the foundations of walls of various types and purposes.
- PIER FOUNDATION – they carry and transfer to the ground the loads of structures that are subjected to concentrated loads, such as columns.
- FOUNDATION BEAM – several pier foundations connected into one linear unit.
- FLAT FOUNDATION – they are constructed under the entire surface of a building when different ground settlements are expected, when the loads of strip foundations or piers in their arrangement would cause soil deformations, or when some parts of the structure are more heavily loaded. They are often used in combination with deep foundations when the bearing soil lies at greater depths.
- FOUNDATION GRID – several foundation bearings mutually perpendicular and connected into a single whole.
2. DEEP FOUNDATIONS – foundations at greater depth due to heavy loads of elements (silos, columns, bridges, etc.), when the soil is not sufficiently bearing, when groundwater is present in the foundation area, or when construction takes place in water. In some cases the depth of foundation reaches 70 m or even more.
- REPLACEMENT OF THE FOUNDATION PRESSURE BELOW THE FOUNDATION – performed when the bearing soil lies deeper than the design depth and there is no groundwater in the soil. The foundation excavation is deepened across the foundation width to the bearing soil, and the deepened portion of the excavation is filled with lightweight concrete or well-compacted gravel.
2. Piles are made of reinforced concrete or steel. They are driven or bored to a depth of the bearing solid soil, thereby transferring the loads. If the bearing soil is too deep, they rely on friction.
3. Piles are structures with which very large forces are transferred to deep foundation layers. They are circular in plan shape, with diameters up to several meters.
