It defined as the depth of foundation is less than or equal to Breadth of foundation. Shallow foundations are generally for 2 to 3m depth
To know the construction of foundation
To know the different types foundations
To know which type of foundation is suitable for
different types soils.
Every structure consists of two parts:
Sub-structure or foundation and
Foundation : It is the lowest part of a structure which
is constructed below the ground level.
The function of foundation is to transmit the
weight of super structure to the sub soil.
TYPES OF FOUNDATIONS
1. SHALLOW FOUNDATIONS (D<= B)
2. DEEP FOUNDATIONS (D>= B)
TYPES OF FONDATIONS
1. SHALLOW FOUNDATIONS
MAT OR RAFT FOUNDATION
2. DEEP FONDATIONS
SAND OR PEIECES OF
P C C
P C C
It is provided under columns to transfer the load safely to
These footings may be slab, stepped or sloped ones.
P C C
A combined footing is the one which supports two columns and it
may be rectangular or trapezoidal in plan.
The aim is to get uniform pressure distribution under the footing.
For this the center of gravity of the footing area should coincide
with the center of gravity of the combined loads of the two
Combined footings are used in the following situations:
When the columns are very near to each other so that their
When the bearing capacity of the soil is less, requiring more area
under individual footing.
When the end column is near a property line so that its footing
cannot spread in that direction.
It is most suitable foundation when the soil at the site
proposed for the construction of a structure is erratic,
soft clay, made up ground or marshy land with low
Mat foundation is constructed of RCC slab covering the
whole area of the bottom of the structure. The slab is
provided with steel reinforcing bars in both directions.
When column loads are heavy, the main beams and
secondary beams are provided monolithically with raft
R C C SLAB
SECTION ALONG AA
Pile foundation is more commonly used in building
Pile foundations are used in the following situations:
The load of the super structure is heavy and its distribution
The top soil has poor bearing capacity
The subsoil water level is high
There is large fluctuations in subsoil water level
Canal or deep drainage lines exist near the foundation
The structure is situated on the sea shore or river bed
END BEARING PILES FRICTION PILES ANCHOR PILESTENSION PILESCOMPACTION PILES
CLASSIFICATION OF PILES
BASED ON FUNCTION
CONCRETE PILES TIMBER PILES STEEL PILES COMPOSITE PILES
CAST-IN SITU PILES
H - PILE
CONCRETE AND TIMBER
CONCRETE AND STEEL
END BEARING PILE : These piles are used to transfer
load through water or soft soil to a suitable bearing
END BEARING PILE
FRICTION PILE: These piles are used to transfer loads to a
depth of a friction load carrying material by means of
skin friction along the length of pile.
COMPACTION PILECOMPACTION PILE
COMPACTION PILE: these piles are used to compact loose soils,
thus increasing their bearing capacity. The compaction piles
themselves do not carry any load.Hence they may be of weaker
material (sand). The pile tube, driven to compact the soil, is
gradually taken out and sand is filled in its place thus forming a
UNDER REAMED PILE
In black cotton soils and other expansive type of
soils, buildings often crack due to relative ground
movements. This is caused by alternate swelling
and shrinking of the soil due to changes in its
The under-reamed pile is used to safe guard this
movement effectively. Generally this foundation is
used for machine foundation, factory building,
transmission line towers and other tall structures
Well foundation is a box of timber, metal, reinforced
concrete or masonry which open both at the top and
bottom, and is used for building for building and bridge
Types of well shapes:
Double – D
Twin circular etc..,
WELL FOUNDATIONWELL FOUNDATION
Factors affecting choice of foundation
The type of construction.
The magnitude of load.
Feasibility in terms of available skilled labors and cost.
The type and bearing capacity of soil.
The seismic hazard and vulnerability of site to
Construction of foundation
Construction of foundation consists upon the
Pour slab on grade
Pour concrete foundation walls
• Remove trees and any debris
• Remove top soil (4-6” below surface)
• Define the boundaries by using chalk powder.
• Layout building perimeter, Establish building
corners & building perimeter.
•Use surveying instruments
•Excavate foundation along line created.
•Excavate remainder of soil inside perimeter
•(Don’t excavate inside soil if slab on
•If deep foundation, taper edges to prevent
•If soil unstable, or very deep - use shoring
•Construct formwork (if required)
•Install reinforcement (rebar) for footing.
•Pour concrete footings
•Smooth / finish surface
Pour Slab on Grade
•Install gravel base (to keep water off of slab)
•Install moisture barrier (to keep water off of slab)
•Install reinforcement (welded wire fabric)
•Pour concrete slab
•Finish slab surface
Pour Concrete Foundation Walls
•Construct formwork (include sleeves /
doors / windows)
•Install reinforcement into formwork
•Pour concrete foundation wall
•Install anchor bolts into semi-cured
Pour Concrete Foundation Walls
•Allow concrete to cure adequately (7-10 days)
Structures Below Ground subject to
penetration of ground water
More extreme, if below H2O table
Two basic approaches to Waterproofing
– Waterproof Membranes, or
– Generally - both used in tandem
– Liquid or sheet (plastic, asphaltic,
– Coatings (asphaltic)
– Cementitious plasters & admixtures
– Bentonite clay
Protecting boards or panels
– Protection board
– Water stop
» Unit of measure - SF, in (thickness)
Stone & Perforated Pipe Drainage Mat & Perforated Pipe
Typically, a liquid asphalt
Applied with a
Roller or sprayer
Not an effective barrier
For water under pressure.
But, will prevent ground
‘Moisture’ from migrating
Through a wall.
Typically used in conjunction
Will drainage pipe.
Underpinning is the process of strengthening the
foundation of an existing building or other structure.
Underpinning may be necessary for A variety of reasons:
The original foundation is simply not strong or stable
The usage of the structure has changed.
The properties of the soil supporting the foundation may
have changed (possibly through subsidence) or were
mischaracterized during design.
The construction of nearby structures necessitates the
excavation of soil supporting existing foundations.
•To increase the depth or load capacity of existing foundations to
support the addition of another storey to the building (above or
•It is more economical, due to land price or otherwise, to work on
the present structure's foundation than to build a new one.
•Earthquake, flood, drought or other natural causes have caused the
structure to move, thereby requiring stabilization of foundation soils
•Underpinning may be accomplished by extending the foundation in
depth or in breadth so it either rests on a more supportive soil
stratum or distributes its load across a greater area. Use of micro
pilesand jet grouting are common methods in underpinning