TYPES OF FOUNDATIONS: Shallow foundation, Deep Foundations.

Foundations may be broadly classified under two heads:

(a) Shallow Foundations
(b) Deep Foundations.

According to Terzaghi, a foundation is shallow if its depth is equal to or less than its width. In case of deep foundaüons. the depth is equal to or greater than its width.

(A) SHALLOW FOUNDATIONS

From the point of view of design, shallow foundations may be of ttic following typcs:

1. Spread footings.
2. Combined footings
3. Strap footings.
4. Mat foundation.


Various types of shallow foundations are shown in Fig. 2.1. A brief description of these is given below.

FIG 2.1 VARIOUS TYPES OF SHALLOW FOUNDATIONS.

(B) DEEP FOUNDATIONS

Deep foundations may be of the following types:

1. Deep strip, rectangular or square footings.
2. Pile foundation.
3. Pier foundation or drilled caisson foundation.
4. Well foundation or caissons. 

As stated earlier, the usual strip, rectangular or square footings come under the category of deep foundations, when the depth of the foundation as more than the width of the footing. Well foundations are generally adopted for bridge piers etc. and not for building foundations.