What buildings are raft foundations used for?
Foundations provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics. Very broadly, foundations can be categorised as shallow foundations or deep foundations.
What is raft foundation preferred?
a) Raft foundations are preferred in areas with poor soil bearing capacity, uneven settlement, and the presence of mixed soil types. These foundations achieves the load-bearing capacity through the distribution of stresses to a larger area.
What is the minimum depth of raft foundation?
The minimum thickness of raft foundation is 300mm.
What are the three types of raft foundation?
There are five main types of raft foundation:
- Solid slab rafts,
- Slab beam rafts,
- Cellular rafts,
- Piled raft foundations; and,
- Balancing (or floating) rafts.
Why do you need a raft foundation?
A raft foundation is a reinforced concrete slab under the whole of a building or extension, ‘floating’ on the ground as a raft floats on water. This type of foundation spreads the load of the building over a larger area than other foundations, lowering the pressure on the ground.
What is the difference between raft and mat foundation?
Usually, mat foundation is spread over the entire area of the structure it is supporting. Raft foundation is generally used to support structures like residential or commercial buildings where soil condition is poor, storage tanks, silos, foundations for heavy industrial equipment etc.
What is the minimum thickness of mat foundation?
The depth of mat foundation must satisfy shear requirements. A uniform thickness can be used for raft foundation if columns are equally spaced and the loads are not very heavy. According to ACI 318-14, British standard; Eurocode 7; and IS 456; a minimum cover of 50 mm is required for mat foundation.