The foundations may be broadly classified as shallow foundation and deep foundation. A foundation is said to be shallow foundation if its depth is equal to or less than its width. When the depth is equal to or greater than its width, the foundation is termed as deep foundation.

## TYPES OF SHALLOW FOUNDATION:

The Shallow foundations are of the following types:

### SPREAD FOOTING:

The spread footing are those which spread the super imposed load of the structure over a large area. The spread footing may be of the following types:

1- Single footing for a column

2- Stepped footing for a column

3- Sloped footing for a column

4- Wall footing without steps and with steps

5- Grillage foundation

The base of first three types of footing is made of concrete. When heavy structural loads from column are required to be transferred to a soil for low bearing capacity, the most economical foundation is Grillage foundation. The depth of such a foundation is limited to 0.9 to 1.6 m.

### COMBINED FOOTING:

**1-**The common footing which is constructed for two or more columns is called combined footing.

**2-**The shape of a combined footing is so proportioned that the center of gravity of the supporting area is in line with the center of gravity of the two column loads.

**3-**The general shape of a combined footing is either rectangular or trapezoidal.

**4-**A combined rectangular footing a provided where loading condition is such that either of two columns are equally loaded or the interior column carried greater load.

**5-**A trapezoidal combined footing is provided under any condition of loading.

### STRAP FOOTING:

**1-**When two or more footings are connected by a beam, it is called a strap footing.

**2-**It may be used where the distance between thee columns is so great that a combined trapezoidal footing becomes quite narrow with high bending moments.

### RAFT OR MAT FOUNDATION:

**1-**A foundation consisting of thick reinforced concrete slab covering the entire area of the bottom of the structure is known as Raft or Mat foundation.

**2-**When is allowable soil pressure is low or the building loads are heavy and if the required area of footing is more than half the total area of the structure, then it is more economical to use raft or mat foundation.

## TYPES OF DEEP FOUNDATION:

The deep foundation are of the following types:

### PILE FOUNDATION:

**1-**A pile is a long vertical load transferring member composed of either timber, steel or concrete.

**2-**In pile foundation, a number of piles are driven in the base of the structure.

**3-**The pile foundation is generally used when the soil is compressible, water logged and made up type.

**4-**It is most suitable for bridges.

### PIER FOUNDATION:

**1-**In pier foundation, hollow vertical shafts are sunk upto the hard bed and hollow portion are then filled up with inert material such as sand or lean concrete.

**2-**The pier foundation are specially suitable for heavy structures such as flyover in sandy soil or soft soil overlying hard bed at reasonable depth.

### CAISSON OR WELL FOUNDATION:

**1-**The open caisson is a box of timber, metal, reinforced concrete or masonry which is open both at the top and at the bottom and is used for building and bridge foundation.

**2-**Out of these three types of deep foundation, pile foundation is more commonly used in construction.

I hope that this article will help you understanding about WHAT ARE DIFFERENT TYPES OF FOUNDATION.

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