The art of
selecting, designing, and constructing the elements that
transfer the weight (Weight may also include horizontal
loads in addition to vertical loads) of a structure to the
underlying soil or rock.
·The term "foundation
engineering" is used to include the design of
foundations for buildings and other structures and also
for such non-foundation problems as designs of retaining
walls, bulkheads, cofferdams, tunnels, and earth dams, as
well as the design of natural slopes, dewatering of soils,
and stabilization of soils mechanically and chemically.
is interfacing element between the superstructure and the
underlying soil or rock. The loads transmitted by the
foundation to the underling soil must not cause soil shear
failure or damaging settlement of the superstructure.
Classification of Foundations
consideration in the foundation design should be the
The data from
such investigations should be evaluated to determine
whether or not the use of a deep foundation is necessary.
studies, together with studies of the soil properties,
reveal that detrimental settlement can be avoided by more
economical methods, then deep foundations should not be
1-Determine the foundation
loads to be supported.
2-Evaluate the subsurface
exploration and elaborator testing programs.
3-Prepare a final soil
profile. Determine soil layers suitable or unsuitable for
shallow foundations or deep foundations. Also consider if
ground improvement techniques could modify unsuitable
layers into suitable support layers.
4-Consider and prepare
or Deep foundations.
5-Prepar cost estimates
for feasible alternative foundation designs including all
associated substructure cost.
6-Select the optimum
Q. Why worry about
A. They hold everything up
Q. What factors does the
Geotechnical Engineer need to consider in selecting a
A. 1. Type of
Structure 2. Loads (how heavy)
3. Type of Ground
(good soil vs. bad soil)
Schedule 5. Cost
The foundation takes the
load from a structure and transmits it to safely to the
Q. What kinds of loads do
we need to worry about ?
A. 1. Compression
2. Tension (upward)
5. Combinations of
Deriving support at or
near the ground surface and are usually used when the load
Pad or column footings
(Isolated or Combined)
Slab on grade with
Interior footings for
Mat (Raft) footings
of Shallow Foundations
Isolated Pad Footings
Mat (or Raft)
consists of one footing
usually placed under the entire building area. They are
used, when soil bearing capacity is low, column loads are
heavy single footings cannot be used, piles are not used
and differential settlement must be reduced.
Mat (or Raft)
Mat (or Raft)
Mat (or Raft)
are those founding too deeply below the finished ground
surface for their base bearing capacity to be affected by
surface conditions, this is usually at depths >3 m below
finished ground level. Deep foundations can be used to
transfer the loading to a deeper, more competent strata at
depth if unsuitable soils are present near the surface.
are used when there are weak (bad) soils near the
surface or when loads are very high, such as very large
derive their support from deeper soils or bedrock
of Deep Foundations are :
foundations are the part of a structure used to carry and
transfer the load of the structure to the bearing ground
located at some depth below ground surface. The main
components of the foundation are the pile cap and the
Pile foundations are
frequently needed because of the relative inability of
shallow footings to resist inclined, lateral, or uplift
loads and overturning moments.
Pile foundations are used
in areas of expansive or collapsible soils to resist
undesirable seasonal movements of the foundations.
are thick slabs used to tie a group of piles together to
support and transmit column loads to the piles.
are long and slender members which transfer the load to
deeper soil or rock of high bearing capacity avoiding
shallow soil of low bearing capacity
long, slender members that transmit foundation loads
through soil strata of low bearing capacity to deeper soil
or rock strata having a high bearing capacity. They are
used when for economic, constructional or soil condition
considerations it is desirable to transmit loads to strata
beyond the practical reach of shallow foundations. In
addition to supporting structures, piles are also used to
anchor structures against uplift forces and to assist
structures in resisting lateral and overturning forces.
are foundations for
carrying a heavy structural load which is constructed
insitu in a deep excavation.
A pier is a
drilled shaft varying in diameter and depth. After the
pier hole is drilled, it is filled with concrete and Steel
reinforcement is sometimes utilized for a portion of the
length of the pier.
a form of deep foundation which are constructed above
ground level, then sunk to the required level by
excavating or dredging material from within the caisson.
Caissons are usually used in construction of bridge piers
and other structure where the foundation is under water.
Compressed air is used to keep water out and allow
installation and construction in dry conditions.
High air pressures have created dangerous air conditions
for workers, who must use an air lock
are deep foundations in
which the relief of stress due to excavation is
approximately balanced by the applied stress due to the
foundation. The net stress applied is therefore very
small. A compensated foundation normally comprises a deep