Construction is a general term used for creating objects. It is a process of delivering buildings, infrastructure, industrial facilities, and associated activities until completion. Construction covers the planning, financials, and design and continues till the project is ready for use. Construction contributes to many countries’ gross domestic product (GDP). Though it brings the most economic benefits, construction is one of the most hazardous industries. A lot of fatalities are associated with construction. For this reason, a strong foundation is a prerequisite for any construction project. This article focuses on mat foundation, which is a very common type of foundation. Before we get into what mat foundation is and its uses, let’s first discuss the basics of construction.
Also read about the significance of Shallow foundation in construction
Construction sectors
There are majorly three sectors for construction:
Buildings
Construction of buildings is generally divided into residential and non-residential.
Infrastructure
Infrastructure is also known as civil engineering and includes dams, bridges, highways, railways, and water utility distribution.
Industrial
Industry often includes offshore construction such as quarrying and mining, chemical processing, refineries, and power generation or manufacturing plants.
Construction process: Steps involved
Some constructions are small design or repair jobs, whereas others are more complex and require outside expertise and a workforce. The construction process is generally as follows:
Planning
A proposed project must comply with the local public land-use policies.
Legal
A project includes a variety of legalities that all parties must consider. Finally, contracts are lined up, a set of obligations between two or more parties.
Finance
Mortgage bankers, accountants, and cost engineers may be employed based on the type of project and participate in creating the overall management of the project financially.
Procurement
A common way of procurement is Design-bid-build. Here the architect, builder, or engineer works for the client as a project manager and manages the works from inception to completion.
Design
The property owner hires a design team, and construction involves translating a design into reality.
Commissioning
It includes checking all the subsystems of the new building work as required.
Liability period
After the handover, the owner may find any shortcomings with the contractor who corrects them.
Repair, maintenance and improvement
Maintenance includes servicing, functional checks, repairing, and any installations.
Demolition
It is the safety and efficient tear down of a building or construction.
What is mat foundation?
A mat foundation is a large continuous rectangular slab that carries the entire weight of a superstructure. This slab spreads underneath the entirety of the building. A mat foundation applies under the footprint of the building and helps reduce contact pressure. It is helpful for high structural loads, soft pockets of soil, and highly compressible soil.
Construction of mat foundations: Materials required
Some materials required for the construction of a mat foundation include:
- Spacer
- Formwork
- Concrete
- Reinforcement
Construction of mat foundations: Steps involved
The following steps are generally followed in the construction of the mat foundations:
- First, a flat level is achieved by removing excess dirt and excavating soil.
- The foundation bed is then compacted by ramming.
- A waterproof plastic is laid over
- 7cm of concrete is poured to create a perfectly flat layer.
- Reinforcement is laid over the flat foundation. The support is provided from both ends in the form of a steel mesh. These steel meshes are laid over and below the foundation to balance the bending forces.
- After laying down the steel reinforcement, concrete of the desired amount is filled in.
- Lastly, a curing regime is completed to help the concrete reach a designated compression strength.
Uses of mat foundations
- Mat foundations are highly used for constructing commercial buildings. This is because loads of buildings are large, and mat foundations are common in places with basements.
- Mat Foundations are also used where there is low bearing capacity soil. This helps to spread the building load and construct a stable foundation evenly.
- It is used in differential settlement of buildings.
- These foundations are heavily used in unstable soil conditions. In such cases, the foundation covers 70% of the ground area beneath the building. Such situations are also encountered in mining areas.
Types of mat foundations
- Flat plate:
A thick concrete slab. There are no projections to thicken the mat foundations.
- Flat plate foundation thickened under the column:
The thickness of the mat foundation is increased below the columns.
- Flat plate foundation thickened above the frat at column:
Construction above the foundation is more accessible.
- Beam and slab raft foundation:
Beams are provided to stiffen the foundation. This reduces the thickness of the foundation.
- Cellular raft foundations:
A top slab is also placed, which further stiffens the mat foundation.
- Pile raft foundations:
This is done in high-rise buildings. Initially, the piles take the load, and once all bundles are in place, the mat foundation takes the load.
Mat foundations design
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Conventional Design Method
The total applied load is calculated in this design method. The shear force and bending are also calculated. Additionally, the reinforcement area per unit is calculated.
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Finite Design Method
In structural analysis, the finite design method is considered. Again, the soil is the model, and its behaviour is incorporated into the study.
Advantages of mat foundations
Mat foundations provide suitable resistance for buildings, thus preventing structures from sliding during floods. In addition, these foundations help transfer the loads and vice-versa. When costs are high, the use of a mat foundation is helpful. Time and materials are taken care of when the mat foundation and ground floor slab are poured in simultaneously. As mat foundations are shallow, there is less digging time required. Therefore, a mat foundation can take more load compared to other foundations. Furthermore, mat foundations can be constructed on poor soil.
Disadvantages of mat foundations
For mat foundations, more quantity of steel or concrete is required. Therefore, mat foundations are not suitable for domestic uses. In addition, for a concentrated load, specific measurements are needed. Generally, the area is significant for mat foundations, and the cost of installing it is higher.
Mat foundation Vs spread footing: A comparison
Both mat foundation and spread footing are types of foundations. However, they have different applications, construction methods, advantages, and disadvantages. A mat foundation is a large slab that supports multiple columns and walls under a large part of or the entire structure. Spread footing, on the other hand, is a square, circular, or rectangular slab that is used to support an individual column.
FAQs
Where are mat foundations commonly used?
Mat foundations are commonly used for buildings with basements. Mat foundations are more cost-effective for buildings covering a large area.
What is the difference between a mat and raft foundation?
A mat foundation is spread over an entire structure. A raft foundation supports residential or commercial buildings in poor soil conditions.
What is the primary purpose of a mat foundation?
A mat foundation helps transfer the entire building load onto the ground.
How deep does a mat foundation go?
The thickness of a mat foundation can vary from one foot to not more than twenty feet. Therefore, the reinforcing system is more substantial.
Why is mat foundation preferred?
When soils have a low-bearing capacity, and the load of the building needs to be handled and transferred to the ground, a mat foundation is preferred. A mat foundation is preferable when other foundations or footing cannot be considered.