Under water foundation technology like caisson foundation, cofferdams and shore piling

1. SPECIAL FOUNDATION TECHNIQUES
UNIT 3
PREPARED BY : SHRIDEVI HUDDAR
ROLL NO. -17
DR. D. Y. PATIL COLLEGE OF
ARCHITECTURE, AKURDI
F. Y. M.ARCH 2020 - 2021

2. FOUNDATIONS
• The lowest artificially prepared parts of the structure which are in direct contact with the ground and
which transmit the loads of the structure to the ground are known as Foundation or Substructure.
• The solid ground on which the foundation rest is called the “foundation bed” or foundation soil and it
ultimately bears the load and interacts with the foundations of buildings.
Objects of foundations:
Foundations are provided for
the following purposes
1) To distribute the total load
coming on the structure on
large area.
large area.
2) To support the structure
3) To give enough stability to
the structures against various
distributing forces such as
wind, rain etc.
4) To prepare a level surface
for concreting and masonry
work.

3. Types of foundations:
Depending upon their nature and depth, foundations have been categorized as follows
i. Open foundations or shallow foundations.
ii. Deep foundations
I. Open foundations or shallow foundations:
• This is most common type of foundation and can be laid using open excavation by allowing natural
slopes on all sides.
• This type of foundation is practicable for a depth of about 5m and is normally convenient above the
water table.
• The base of the structure is enlarged or spread to provide individual support. Since the spread
foundations are constructed in open excavations, therefore they are termed as open foundations.
• This type of foundation is provided for structure of moderate height built on sufficiently firm dry
ground.

4. The various types of spread footings are:
1. Wall footing
2. Isolated footing
3. Combined footing
4. Inverted arch footing
5. Continuous footing
6. Cantilever footing
7. Grillage footing
1. Wall Footing: These footings can be either simple or stepped.
2. Isolated Footings: These are used to support individual columns. They can be of stepped type or have
2. Isolated Footings: These are used to support individual columns. They can be of stepped type or have
projections in the concrete base.
3. Combined Footing: A combined footing supports two or more columns in a row. A Combined footing
may be rectangular or trapezoidal constructed with reinforced concrete.
4. Inverted Arch Footing: This type of construction is used on soft soils to reduce the depth of
foundation loads above an opening are transmitted from supporting walls through inverted
arches to the soil.

5. 5. Continuous Footing: In this type of footing a single continuous
R.C.C slab is produced as foundation of two or three or more
columns in a row.
6. Strap or cantilever footing: Strap footing consists of two or more
individual footings connected by a beam called strap or cantilever
footing or pump handle foundation.
7. Grillage footing : This type of footing is used to transmit heavy
loads from steel columns to foundation soils having low bearing
power.
8. Raft Foundation: A raft or mat is a combined footing that covers
8. Raft Foundation: A raft or mat is a combined footing that covers
the entire area beneath a structure and supports all the columns.
Raft Foundation
Strap or cantilever footing

6. II. Deep foundations:
• These foundations carry loads from a structure through weak compressible soil or fills onto the
stronger and less compressible soils or rocks at depth.
•These foundations are in general used as basements, buoyancy rafts, caissons, cylinders, shaft and
piles.
a) Basements: There are constructed in place in an open excavation.
They are hallow slab structure designed to provide working or
storage space below ground level. The structural design is
governed by their functional requirements.
b) Buoyancy rafts: They are hallow substructures designed to
b) Buoyancy rafts: They are hallow substructures designed to
provide a buoyant substructure beneath with the net loading on
the soil reduce to the desired low intensity.
c) Caissons: They are hallow substructures designed to be
constructed on or near the surface and then sunk as single units to
their required level.
d) Cylinders: They are small single cell caissons
Buoyancy rafts

7. e) Shaft foundations: They are constructed within deep
excavation supported by lining, constructed in place subsequently
filled with concrete.
f) Pile foundations:
• Pile foundation is a construction for the foundation supported
on piles.
•A pile is an element of construction composed of timber,
concrete, or steel or a combination of them.
• Pile foundation may be defined as a column support type of a
foundation, which may be cast in-situ or Pre-cast.
• This type of construction is adopted when the loose soil extends
to a great depth.
• The load of the structure is transmitted by the piles to hard
stratum below or it is resisted by the friction developed on the
sides of pipes.

8. (i) Classification based on the function
a) Bearing piles- Penetrate through soft soil and their bottom rest on a hard stratum
b) Friction piles- This type of pile utilizes the frictional resistance force between the pile surface and
adjacent soil to transfer the superstructure load
Friction pile Bearing pile
c) Screw piles- Used for gravely ground sand, mixed gravel
ground etc
d) Uplift piles- when the structure subjected to uplift
pressure.
e) Butter pile - To resist large horizontal or inclined forces
f) Sheet pile- used as bulk heads or a impervious cut off

9. (ii) Classification based on materials and composition
a) Cément concrète piles- Posses excellent compressive
strength
1) Precast
2) Cast-in-site
a) Under reamed piles
b) Bored compaction piles
b) Timber piles- Small bearing capacity, not suitable for
hard soil and economical
c) Steel piles- With stand impact stresses and resist
lateral
lateral
forces
d) Sand piles- Not suitable for loose or wet soils or where
is
a danger of scour. Easy to construct and irrespective of
water table.
e) Composite piles- combination of two different
materials
are used to form composite file and suitable where the
upper part of pile to project above the water table.
Economical and easy to construct
Precast Concrete Piles

10. Special Foundation :
Section 20 of the Party Wall Act defines 'Special Foundations' as : "foundations in which an assemblage
of beams or rods is employed for the purpose of distributing any load“
Following are the Special Foundations I have covered , They are :
1. Caisson Foundation
2. Cofferdam Foundation
3. Shore Piling Shore Piling
3. Shore Piling
Caisson Foundation
Cofferdam Foundation

11. CAISSON
• Caisson is a watertight retaining structure used, for example, to work on the foundations of
a bridge pier, for the construction of a concrete dam, or for the repair of ships.
• Caissons are constructed in such a way that the water can be pumped out, keeping the work
environment dry.
• When piers are being built using an open caisson, and it is not practical to reach suitable
soil, friction pilings may be driven to form a suitable sub-foundation.
• These piles are connected by a foundation pad upon which the column pier is erected.
• The main functions of caissons are soil or water retention and transfer of vertical and
horizontal loads into the subsoil strata.
horizontal loads into the subsoil strata.
TYPES OF CAISSON :
1. Box Caisson
2. Open Caisson
3. Monolithic Caisson
4. Pneumatic Caisson

12. Box Caisson
• A box caisson is a prefabricated concrete box
(with sides and a bottom); it is set down on
prepared bases.
• Once in place, it is filled with concrete to
become part of the permanent works, such as
the foundation for a bridge pier.
• Hollow concrete structures are usually less
dense than water so a box caisson must be
ballasted or anchored to keep it from floating
until it can be filled with concrete.
Open Caisson
• An open caisson is similar to a box caisson,
except that it does not have a bottom face.
• It is suitable for use in soft clays (e.g. in
some river-beds), but not for where there
may be large obstructions in the ground.
• An open caisson that is used in soft grounds
or high water tables, where open trench
excavations are impractical, can also be used
to install deep manholes, pump stations and
reception/launch pits for micro tunnelling,
until it can be filled with concrete.
• Sometimes elaborate anchoring systems may
be required, such as in tidal zones.
reception/launch pits for micro tunnelling,
pipe jacking and other operations.

13. Pneumatic Caisson-
• Pneumatic Caisson is open at the bottom side and
closes at the top side.
• Pneumatic caisson is specially used at the place
where it is not possible to construct well.
• It is suitable where the depth of water is more than 12
m.
• In the construction process of the pneumatic Caisson,
the compressed air is used to remove water from the
working chamber and the foundation work is carried
working chamber and the foundation work is carried
out in the dry condition.
• The process of the Construction of the pneumatic
Caisson is the same as the open Caisson.
• The Quality Control in the Pneumatic Caisson is good
because the work is done in the dry conditions.
• Pneumatic Caissons are more expensive as compared
to the Open Caisson.

14. Construction Method of Caisson Foundation
There are various methods by which Caissons are installed into the ground, they are as
follows :
1. Prefabrication of Caisson
2. Transportation of the Caisson
3. Positioning and Immersion of Caissons
4. Ballasting
1. Prefabrication of Caisson :
• Firstly, the caissons are generally prefabricated near the Construction site or at any other
suitable location.
• After prefabrication of the Caissons, they are tested for the water tightness.
• In the tests, the Caissons are check for any leakages and, if found they are repaired
immediately.

15. 2. Transportation of the Caisson
• Then the Caissons are transported to the required location.
• The transportation of the Caisson should be done by following all precautionary measures.

16. 3. Positioning and Immersion of Caissons
• It is very important that Caisson should be properly positioned at the desired place.
• The final positioning of a caisson is achieved with the help of tug boats or with cables from
floating equipment and anchors or dead-man beds.
• When the caisson is ready, the soil is dug from the work chamber which causes the caisson
to subside into the ground.
• Traditionally the excavation is done by the hands but nowadays the sand pumps and other
machinery are used for the excavation.
• The excavated soil is removed with the help of a hydraulic transport system.
• The Caisson is subsided under its own weight.
• When the caisson has reached the desired depth, then the work chamber is completely
• When the caisson has reached the desired depth, then the work chamber is completely
filled with the Concrete.
• This prevents further sinking of the Caisson.

17. 4. Ballasting
• After the immersion of the Caisson, they are ballasted.
• The main function of the dump of rubble at the side of the caisson is to prevent it to slide
away and helps to maintain maximum stability.
Advantages of Caissons Foundation
• Excavation and the process of concreting can be done in dry conditions
• Caissons are good in the lateral as well as axial loading capacity.
• Caisson is highly adaptable in different site conditions.
• Caissons are economical as compared to traditional foundation.
• Caisson can be inserted at any place.
• It is strong enough to withstand the moments and loads applied to the structure.
• Caisson does not require pile caps, because it is filled with concrete.
• Caissons have a large cross-sectional area which helps to resist the scouring effect.
• Caissons can be extended up to the large depths in the ground.

18. • The Inspection and cleaning at
the bottom of the Caisson are difficult.
• There is a lack of skilled workers
which are required for the construction
of the Caisson Foundation.
• Caissons can not be construed in the
contaminated sites.
• Caissons are required to
Disadvantages of Caisson Foundation
• Caissons are required to
be constructed under the supervision
of the Experts.
• There may be a risk to the workers to
get affected by the caisson diseases. So
the proper health control is essential.
• The limit for the depth of
the penetration of the Caisson is up to
35 m.

19. Application of Caisson Foundation in Civil Engineering
• It is used in the construction of piers of the bridges in the water bodies.
• Caisson is also used in the construction of large and Multi-Floor Buildings.
• Caissons provide a platform for installation of machineries and pumps below the
ground level.
• Pneumatic Caissons are used in the construction of railway bridges.
• Caissons are also used to provide access to the shaft and tunnels.

20. COFFERDAM
• A cofferdam is an enclosure built within a body of water to allow the enclosed area to be
pumped out.
• This pumping creates a dry working environment so that the work can be carried out safely.
• Cofferdams are commonly used for construction or repair of permanent dams, oil platforms,
bridge piers, etc., built within or over water.
• These cofferdams are usually welded steel structures, with components consisting of sheet
piles, Wales, and cross braces.
• Such structures are usually dismantled after the construction work is completed.
• Cofferdams are made by driving sheet piling, usually steel in modern works, into the bed to
form a watertight fence. The vertical piles are held in place by horizontal framing members
that are constructed of heavy timber, steel, or a combination of the two.

21. Types of Cofferdams and Their Construction Details
Coffer dams can be classified into many types depending upon the depth, soil conditions, and
fluctuations in the water level and type of material used.
Types of Cofferdams
Considering the material used in their construction, cofferdams may be divided into the
following categories.
1. Earthen cofferdam
2. Rockfill cofferdam
2. Rockfill cofferdam
3. Single-walled cofferdam
4. Double-walled cofferdam
5. Braced cofferdam
6. Cellular cofferdam
(Circular or diaphragm type)

22. • Earthen cofferdams are constructed at the place where the height of the water is less say 3m
and the current velocity is low.
• These dams are built using the local available material such as clay, fine sand or even soil.
• The height of the dam is kept 1m more than that of max water level.
• Freeboard of the dam or the top of the dam is kept 1m so that the water doesn’t enter the
other side even when waves arise.
• The slope is usually given but 1:1 or 1:2. The slope of the water side is pitched with rubble
stones so the water action doesn’t score the embankment.
• Even sheet piles are driven in the center of the dam to resist water seepage.
• After the construction of earthen cofferdam, the water from the other site is pumped out
Earthen Cofferdam
• After the construction of earthen cofferdam, the water from the other site is pumped out
and construction is executed.

23. Rock fill Cofferdam
• Rock-fill cofferdams are better than that of earthen dams.
• These dams are preferred when the rock is available easily at the construction site.
• These dams are very pervious, to prevent water from seeping an impervious membrane of
soil is provided in the dam.
• The height of the dam is can be up to 3m.
• The slope can be maintained at 1:1.5 to 1:125.
• The slope on the water side is pitched so as to protect dam from wave action.

24. Single-Walled Cofferdam
•This type of cofferdam is preferred when the
depth of the water is more than 6m and area of
construction is less. Usually this is used in
construction of bridges.
• Wooden or timber sheets are driven into the
river bed on the perimeter of the area of
construction.
• On the inside steel or iron sheets are driven into
the river bed.
the river bed.
• This inside sheets are placed at equal distance
with the help of wales which are bolted to both
sheets for either sides.
• To improve the stability of this types of dam, half-
filled bags of sand are placed on the both side of
the walls.
• The water from the inside is pumped out and the
construction process is undertaken.

25. Double-Walled Cofferdam
• Double-walled types of cofferdams are used
when the area of construction site is large
and depth of water is high.
• In this place use of single walled cofferdam
becomes uneconomical as the supports are to
be increased. So double walled cofferdam is
used.
• The difference in one wall and double wall
dam is that her it has two walls instead of
walls for extra stability. This type of dams can
walls for extra stability. This type of dams can
hold water up to 12m high.
• Two piles are driven inside the water bed
with a space in between and attached each
other with wales with bolted connection.
• As the water depth increases the space
between the walls increases.
• The space between the walls are filled with
soil. To prevent the leakage from the ground
below, the sheet piles are driven to a good
depth in the bed.

26. Braced Cofferdam
• When it’s difficult to drive piles inside the bed in
the water, then this type of cofferdam is used.
• In braced cofferdam two piles are driven into the
bed and they are laterally supported with the help
of wooden cribs installed in alternate courses to
form pockets.
• The empty pockets here are filled with stone and
earth.
• The framework of the cofferdam (made from, logs
of wood) is prepared on ground and then floated to
of wood) is prepared on ground and then floated to
the site where the cofferdam is to be constructed.
• The layers of sand and the other loose material
overlying the impervious hard bed is dredged out.
• Crib is then sunk to the position, the bottom of
each crib is given a shape to fit in the variation in
the surface of bedrock.
• After the pit is dewatered, the structure is
concreted. When concreting has been completed
above the water level, the cofferdam is removed.

27. Cellular Cofferdam
• When the water layer is more than 20m, common
types of cofferdams are uneconomical to use.
• In this situations cellular cofferdams are used.
• This type of dam is used in construction of dams,
locks, weirs etc.
• Cellular cofferdam is made by driving straight web
steel sheet piles, arranged to form a series of
interconnected cells.
• The cells are constructed in various shapes and
styles to suit the requirements of site.
styles to suit the requirements of site.
• Finally, the cells are filled with clay, sand or gravel to
make them stable against the various forces to which
they are likely to be subjected to.
The two common shapes of the cellular cofferdam
are,
(i) Circular type cellular cofferdam.
(ii) Diaphragm type cellular cofferdam.

28. (i) Circular Type Cellular Cofferdam
• This type of cellular cofferdam consists of circular
arcs on the inner and outer sides which are connected
by straight diaphragm walls.
• The connection between the curved parts and the
diaphragms are made by means of a specially
fabricated Y-element.
•The cofferdam is thus made from interconnected steel
sheet piles.
• The empty spaces are filled with non pervious
materials like clay or sand. Due to the filling material
the self weight of the membrane increases and leakage
the self weight of the membrane increases and leakage
is reduced.
• One advantage of the diaphragm type is that the
effective length of the cofferdam may be increased
easily by lengthening the diaphragm.
• Hence in case, from design consideration it is
necessary to have effective width of the cofferdam
more than 21 meter, diaphragm type of cofferdam
must be used.

29. (ii) Diaphragm Type Cellular Cofferdam
• It consists of a set of large diameter main circular
cells interconnected by arcs of smaller cells.
• The walls of the connecting cells are perpendicular
to the walls of the main circular cells of large
diameter.
• The segmental arcs are joined by special T-piles to
the main cells.
• The circular type cellular cofferdams are self-
sustaining, and therefore independent of the adjacent
circular cells.
• Each cell can be filled independently.
• Each cell can be filled independently.
•The stability of such cells is much greater as
compared with that of the diaphragm type.
• However, the circular cells are more expensive than
the diaphragm type, as these require more sheet piles
and greater skill in setting and driving the piles.
• Because the diameter of circular cells is limited by
interlock tension, their ability to resist lateral pressure
due to high heads is limited.

30. STUDY OF SPECIAL FOUNDATION USED IN MY LIVE CASE STUDY
INDRAPRASTHA PLUS

31. Special Foundation used in Indraprastha + (Live Case Study)
As the building required a space for parking, the location of the site is in such a compact
place, that to provide parking for tenants – builder planned for Basement
• Soil test was done to know the hard strata.
• Builder has Planned for Double basement as per the parking requirement.
• As per the soil test , 8m deep soil and then hard strata.
• Existing building (neighbor plot) foundation was upto 4m.
• So it was clear that , if excavation starts the neighboring buildings will collapse from all 3
sides, as plot is to excavate till 10m deep. As there is no margin between plots.
sides, as plot is to excavate till 10m deep. As there is no margin between plots.
• GLOBAL GEOTECHNICS – Consultant , issued a design of Pile foundation (Shore Pile)
Method obtained for construction of pile :
• It was not possible to excavate 10m deep at one stretch because of many limitations.
• The ground was excavated 3m deep , then piling procedure took place .
• Then 45 degree Anchor piling was done, and this procedure repeated till the actual
excavation level achieved.
• Then 100mm PCC was done all over the ground.
• Raft foundation on PCC and then normal footing work started.
• Work was started on 24/07/2018 and completed on 22/04/2019 . Almost 9 months.

33. 10 M
Shore piles 45 Anchor Pile

35. SHORE PILING
• Shore Piling is a measure to anticipate ground subsidence while unearthing for profound
establishment of a super structure.
• Additionally named as shoring, that might be indicated as brief supporting used to
counteract something, for example, a passage, channel, soil or divider from breakdown
Necessity of Shore Pile
At the point when the dividers of a structure creates
indications of inclining outwards or protruding at that
indications of inclining outwards or protruding at that
point shore heaping is required to avoid further rot
Shoring might be basic to offer help to the dividers of
two nearby structures when the middle of the road
building is to be pulled down or modified.
Shoring is usually utilized when introducing the
establishment of a building. Shore heaps will bolster
the encompassing burdens until the underground
degrees of the structure are built.

36. Types of Shoring Systems
• Sheet Pile
1. Contigous
2. Secant Shore
• Shore Pile
1. Rebar
2. I-section
• Diaphragm wall
1. Cantilever
2. Anchored
Advantages of Shore Piling
• Preventing surrounding structure or soil from collapsing.
• Protecting from seismic waves.
• Providing support to superstructures
Disadvantages of Shore Piling
• Shore piling is uneconomical.
• Piling operation creates noisy environment.
• When excavated deep, shore pile may get collapse
1. Cantilever
2. Anchored
3. Strutted

37. Rock Anchoring
• In the event that the uncovering profundity or
additional charge is higher, cantilever shore heap
should be secured at one or different levels.
• The cantilever heap in this way acts like a
propped cantilever, along these lines lessening
the most extreme bowing minute and thus littler
measurement heap can be received.
• In any case, this includes extra expense of
securing.
• Mourner bars are given to move the heap from
• Mourner bars are given to move the heap from
the heaps to the grapples.
• The grapples are by and large prestressed and
rock stays are more productive than soil grapples.
• The firmness of these grapples ought to be
reasonably appointed in the diagnostic models,
as these are yielding sort of supports.
• Pre-focused on safe havens if there should arise
an occurrence of profound storm cellar
developments are exorbitant.

38. Methodology of Rock Anchoring
• Rock anchors are driven into hard rock
length for holding up shore pile.
• After drilling rock anchor placing of steel
bars or strands takes place.
• Rock anchors hard rock length is then
grouted using suitable grouting material as
per the consultant .
• Once the grout material has attained its
strength, then the strands are stressed
using stressing machine up to the design
using stressing machine up to the design
anchor lock force .
• After rock anchoring is completed, wailer
beam is fabricated using standard channel
for holding up shore pile.
•These inclined rock anchors are provided
at different levels as per the site condition

39. CONCLUSION
Underground basement construction for providing parking of vehicles are becoming common,
therefore in order to prevent surrounding soil from decay shore pile is used commonly as a
temporary retaining structure. This research was conducted to study necessity of shore piling
and its supporting structure (rock anchoring).