Types of Shallow Foundation
In spite of moving deep into the ground, Shallow foundation delivers the load of the structure adjacent to the surface. This type of foundation is mostly found in the areas where digging deep into the ground is impossible and the structure is not heavy. On the other hand, the soil on which the construction of foundation will be done should contain sufficient bearing strength and not be collapsible types. The depth of shallow foundation is under its width.
The shallow foundation is classified on the basis of loading type and site condition.
Strip Footing: This footing contains highest length and lowest breadth. It is also known as wall footing. It has similarity with shallow foundation. It is a comparatively small strip of concrete that is set into a trench and reinforced with steel.
This type footing is generally applied for the foundations of load bearing walls or supports a slab as well as to provide support to the entire length of a long wall. In case the spacing among the adjacent columns is very less, strip footing can be utilized as a low cost alternative.
Spread Footing: Spread footing alias Isolated footing disperse the load of the column or wall through wider area. It may come in various shapes like rectangular, circular, stepped or slopped to distribute the load to greater area.
Combined Footing: If the gapping among two columns is less, two individual spread footing will overlay and thus combined footing is formed. It is performed to allocate the load of two columns uniformly through the footing. Combined footing may come in different shapes like rectangular or trapezoidal in plan.
Strap Footing: It is also called cantilever footing. It unites two isolated spread footings with a flexible strap of cantilever beam that is not in touch with soil.
The rigid strap disperses the load to the soil maintaining equal and consistent soil pressure under the footings of both the columns. It is very economical.
Mat Footing: This footing is formed for the entire area. It appears as a floor having thick reinforced concrete slab similar to a mat or raft.
Mat footing is very effective when acceptable soil pressure is low. When the adjoining columns and walls are nearer, individual spread footing is not possible, then Mat footing is economical.