There are different foundation types and uses of these depends on the soil condition and loads from the structure. It is advisable to know suitability of each foundation types before making any decision for their selection in any construction project.
Following are the foundation types and their uses:
1. Spread footings and wall footings:
Spread footings are those whose base is more wider than a typical load bearing wall foundations. This is used in case of buildings. The wider base of this footing type spreads the weight from the building structure over more area and provides better stability.
Spread Footing
 |
| Spread Footing |
Spread footings and wall footings are generally used for individual columns. walls and bridge piers. These footings are used where the bearing soil layer is within 3m (10 feet) from the ground surface. The soil bearing capacity must be sufficient to support the weight of the structure over the base area of the structure.
These foundations should not be used on soils where there is any possibility of ground flow of water above bearing layer of soil which may result in scour or liquefaction.
2. Mat Foundations:
Mat foundations are those which are spread across the entire area of the building to support heavy structural loads from columns and walls.
Mat Foundation
 |
| Mat Foundation |
The use of mat foundation is for columns and walls foundations where the loads from the structure on columns and walls are very high. This type of foundation is used to prevent differential settlement of individual footings, thus designed as a single mat (or combined footing) of all the load bearing elements of the structure.
This type of foundation is suitable for expansive soils whose bearing capacity is less for suitability of spread footings and wall footings. This type of footing is economical generally when one-half area of the structure is covered with individual footings and wall footings is provided.
These foundations should not be used where the ground water table is above the bearing surface of the soil. Use of foundation in such conditions may lead to scour and liquefaction.
3. Pile Foundations:
Pile foundation is a type of deep foundation which is used to transfer heavy loads from the structure to a hard rock strata much deep below the ground level.
Pile Foundation
 |
| Pile Foundation |
Pile foundations are used to transfer heavy loads of structures through columns to hard soil strata which is much below ground level and where shallow foundations such as spread footings and mat footings cannot be used. This type of foundation is also used to prevent uplift of structure due to lateral loads such as earthquake and wind forces.
Generally used for soils where soil conditions near the ground surface is not suitable for heavy loads. The depth of hard rock strata may be 5m to 50m (15 feet to 150 feet) deep from the ground surface. The pile foundations resists the loads from structure by skin friction and by end bearing. Use of pile foundations also prevents differential settlement of foundations.
4. Drilled Shafts:
Drilled shafts is also a type of deep foundation and has action similar to pile foundations discussed above, but are high capacity cast-in-situ foundations. It is also called as caissons. It resists loads from structure through shaft resistance, toe resistance and / or combination of both of these. The construction of drilled shafts or caissons are done using an auger.
Drilled Shafts or Caisson Foundation
 |
| Drilled Shafts or Caisson Foundation |
This foundation can transfer column loads larger than pile foundations. It is used where depth of hard strata below ground level is location within 10m to 100m (25 feet to 300 feet). This foundation is not suitable when deep deposits of soft clays and loose, water-bearing granular soils exists. It is also not suitable for soils where caving formations are difficult to stabilize, soils made up of boulders, artesian aquifer exists.
