Correct Answer - Option 4 : Beam and slab construction
Concepts:
Mat foundation is also known as the raft foundation. It is a continuous thick reinforced concrete slab on the soil that covers all the area of the ground of the structure like a floor.
Types of Mat Foundations:
1. Flat Plate Raft:
A flat plate raft is used in the small and lightweight load structure. This type of foundation is suitable when the soil is not compressible. The reinforcement bars are provided in directions, top and bottom, in the form of a mesh (cage).
2. Thickened Plate Under Columns:
In this, the thickness of the RCC slab is increased to a certain extent. It is suitable where the column loads are very high and the flat plate raft is not efficient.
3. Slab and Beam Construction:
In this type of mat foundation, beams are placed in perpendicular directions, and all the beams are connected by an RCC slab. The columns are placed at the intersection of beams. It is suitable when the columns are carrying unequal loads and the spacing is large between them.
4. Piled Raft Foundation:
Piled raft foundation is supported by piles in the soil. They are suitable for high compressive soils, where the water table is high in tall buildings.