What is Mat Foundation | Functions, Types, Advantages of Mat Slab Foundation

What is Mat Slab Foundation?

A raft foundation is similar to a mat foundation. In most cases, it is a continuous slab sitting on the ground on which all of the structure’s columns and beams are built.

The mat foundation transfers the entire load of the building or structure to the soil. The mat foundation is employed if the soil condition is particularly poor.

It distributes the entire load from the superstructure to the soil at the same time. The soil area beneath the mat foundation is not crumbling as a result of this.

Because the stress under the soil area is the same for all zones. A mat foundation is ideal for the basement. We employed a mat foundation where one column overlapped another column.

Functions of Mat Foundation:

• Transfer superstructure loads and disperse them across the whole footprint of the building.
• Reduce differential settlement of structures built on unstable ground.

Types of Mat foundation:

The types of mat foundation commonly employed are:

1. Flat plate mat

A flat raft is a thick concrete slab laid as the foundation on the soil.

Apart from the concrete shear walls, there are no projections to reinforce the mat base.

2. Plate thickened under columns

• Increased axial stresses on the column result in increased bending and shear reinforcements.
• It leads to a rise in building costs. We must also expand the thickness of the mat base beyond a certain point.
• It will not be a cost-effective solution to increase the thickness of the entire mat foundation.
• As a result, the thickness of the mat foundation beneath the columns is increased. Construction may be challenging because the protrusion is below the flat plate.
• Placing the reinforcing, waterproofing, and other elements could be difficult.

3. Two-way beam and slab

Beams are set in perpendicular directions in this form of mat foundation, and an RCC slab connects all of the beams. The columns are positioned at the crossroads of the beams.

When the columns are supporting unequal loads and the spacing between them is large, a two-way slab and beam raft foundation is appropriate.

4. Plate with pedestal

This mat serves the same purpose as a thickened flat plate under columns. At the base of the columns, mat pedestals are supplied.

5. Rigid frame mat

When the columns are under a lot of loads, a rigid frame mat is used. The basement RCC wall serves as a deep beam or ribs in rigid frame mat construction.

The rigid frame raft is employed if the foundation depth is greater than 90 cm.

6. Piled Raft

Piles in the ground support this foundation. The stacked raft foundation is appropriate for high-compressibility soils with a high water table. High-rise buildings are typically built on piled raft foundations.

Advantage of Mat Slab Foundation:

• Because of its high resistance, the building will not slide during a flood.
• The mat slab foundation can assist in transferring the building’s load to a more stable place.
• We built a mat slab foundation to produce an economical construction, such as when the cost of a deep foundation is higher than the cost of a shallow foundation.
• We may save money on materials with this mat slab foundation because the foundation is built at the same time as the ground floor slab is poured, which saves both time and money.
• Because the mat slab is a shallow foundation, the foundation’s depth is reduced, and the foundation’s excavation is reduced.
• The load capacity of the mat slab foundation is greater than that of the other types of foundations.
• Another advantage of the mat slab foundation is that it can be built on poor soil.

Disadvantages of Mat foundation

• Mat foundations may require considerable reinforcement in specific sections, which might increase the cost of production.
• If not properly cared for, the edges of the mat base may disintegrate with time. These edges, on the other hand, can last as long as the building they support if properly maintained.
• The design can become exceedingly complex at times, necessitating the use of highly skilled and experienced engineers and employees. When a builder does not have access to skilled personnel, this can be an issue.
• The creation of the mat can be harmed by frost.

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