The document discusses different types of foundations. It describes foundations as the lowest part of a structure that interfaces with the soil. There are two main types: shallow foundations which spread loads laterally with a depth to width ratio of less than 1, and deep foundations which distribute loads vertically with a ratio over 4. The purpose of all foundations is to transfer structural loads to the soil without causing failure or excessive settling.

1. FOUNDATION
The foundation of a structure is the
lowest part of the sub-structure
interfering with the soil and the
structure. It consists of some structural
element (pad or base) the soil
underneath.

2. FOUNDATION ENGINEERING
Foundation engineering is the branch of civil
engineering which deals with the following
two types of problems
 Evaluation of the ability of soil or bearing
capacity of soil.
 Decision of the proper type of footing, size of
footing and at what depth it should be placed.

3. PURPOSE OF FOUNDATION
 The purpose of foundation is to transfer the
load of the structure to the underlying soil
without causing the danger of failure in shear
and excessive settlement.

4. CLASIFICATION OF FOOTING
1. Shallow foundation
Depth/Width < 1
2. Deep foundation
Depth/Width >4
 Shallow foundations spread the load
laterally
 Deep foundations distribute the load
vertically rather than horizontally.

5. TYPES OF FOUNDATION
 STRIP FOOTING
It is simply the enlargement of the bottom of
the wall that will sufficiently distribute the load
to the foundation soil.
When length to the width ratio of
bearing area is greater than or equal to 10,
this type of footing is called “strip footing”.
L/B > 10

6. STRIP FOOTING
 This type of footing displays essentially one
dimensional action, cantilevering out on each
side of the wall.

7. TYPES OF FOUNDATION
 SPRAED OR ISOLATED OR
INDIVIDUAL FOOTNGS
Spread footings are square or rectangular pads that
distribute the column load to an area around a
column i.e.; these support only one column. These
are most commonly used type of shallow footings
because they are usually more economical. A
spread supports one column or one wall.

8. SPRAED OR ISOLATED OR
INDIVIDUAL FOOTNGS
 These may be
a) Isolated or Individual footing
b) Stepped Footings
c) Tappered Footings
 It is used to support the load of a single
column. These are provided where loads
are relatively light and columns are far
spaced.

9. COMBINED FOOTINGS
 A combined footing is a long footing
supporting two or more columns in one row.
Such a footing is often used when one
column is closed to the property line, also
when the loads are heavy and the isolated
footing overlaps.

10. COMBINED FOOTINGS
 The shape of the footing is normally rectangular but
trapezoidal footings are also used if loads from two
columns are different or if one column lies on the
property line for the even distribution of stress.
 If combined footings are designed on the basis that
line of action of the resultant must coincide with the
centroid of the footing. By the provision of combined
footing the risk of differential settlement is reduced.

11. STRAP FOOTING
(Concreted or cantilever footing)
 If two isolated footings are connected by a
beam then this whole assembly is called
‘strap footing’.
 When footings are at different level, they can
also be joined by a strap.
 A strap footing is used to connect an
eccentrically loaded column footing to an
interior column.

12. RAFT OR MASS OR MAT
FOOTING
 A mat footing is a large footing usually
supporting several columns in two or more
rows. If there are a number of columns, and
footings for most of the columns overlap in
both the directions, then we provide a single
footing for all the columns. This type of
footing is called a ‘mat footing’.

13. RAFT OR MASS OR MAT FOOTING
 If the sum of the areas of individual footings
is greater than the half of the total area of the
building, it is economical to provide a raft
footing.

14. FLOATING FOUNDATIONS
 Where the basement is constructed, then the
weight of the overburden soil is reduced, the
balance is obtained by floating foundation.

15. GRILLAGE FOOTING
 It consists of a single or double tier of steel
beams. The top tier is laid at right angle to
the bottom tier. The beams are encased by
concrete. It is suitable for single column load.

16. PILES
 If bearing capacity of the upper soil layer is
insufficient for a spread foundation but firmer
strata is available at greater depth then the
piles are used to transfer the load to the
deeper layer.

17. COMPARISON B/W SHALLOW &
DEEP FOUNDATION