It will explain the details of Well foundation with an example of a case study.

3. • Well foundations are those types of cassion foundation that falls under
the category of deep foundation.
• The word cassion is native to French, meaning a chest or box.
• Deep foundations are opted when there is a need for resistance to
heavy loading by the structure.
• The cassion foundations are of three types.These are as follows:
• Box Cassions
• Open Cassions ( wells )
• Pneumatic Cassions

4. • The origin of well foundations credits back to prehistoric Indian
engineering. The use of well foundations in India hits back to
hundreds of years ago for providing deep foundation beneath the
water level for monuments, bridges and aqueducts. Most promising
example can be use of well foundation in Taj Mahal.

5. • Box cassions are open at top and closed at the
bottom and they are made up of timber, reinforced
concrete or steel. They are built on land, then
launched and floated to pier site where they are
sunk in position. The suitability of these
foundations is confined only to those areas where
the bearing stratum is available at shallow depth,
and where loads are not very heavy.

6. • Open cassion foundations are boxes of timber, metal,
reinforced concrete or masonry which is open at top
and bottom. They are used in constructing the
foundations of bridges and buildings. As they are
similar to wells, they are termed so. It is the most
widely used foundation type in India for construction
of bridges and water house abutments.

7. • These are bit different from the above
mentioned types because the bottom of
foundation is designed as working
chamber in which compressed air is
forced to prevent the entry of water and
thus permit excavation in dry.

8. The shapes of well foundation vary with the requirements
• Single Circular well foundation
• Twin Circular well foundation
• Dumb-well foundation
• Double- D well foundation
• Twin Hexagonal well foundation
• Twin Octagonal well foundation
• Rectangular well foundation

9. • Economics
• Minimizes pile cap needs
• Slightly less noise and reduced vibrations
• Easily adaptable to varying site conditions
• High axial and lateral loading capacity

10. • Extremely sensitive to construction procedures
• Not good for contaminated sites
• Lack of construction expertise
• Lack of Qualified Inspectors

12. 1. Well Cap – It is a RCC slab. Its function is to
transmit the forces from the piers to the body of
well. It is important that the dimension of well
cap should be sufficient to accommodate pier.
2. Top Plug – Top plug is situated below the well
cap. This helps transferring the load through the
granular material into the steining.
3. Steining – Steining is a wall that is built over a
wedge shaped portion called well curb. The wall
should be designed such that it can be sunk
under its own weight. Moreover, the thickness
should be enough to overcome the skin friction
during sinking.

13. 4. Well Curb – As mentioned earlier, the well curb supports the steining.
Well curb is made up of RCC with steel cutting edge.
5. Cutting Edge – The cutting edge is that part of the well which helps in
penetrating the strata of soil. Thus in case of hard strata such as gravels,
the flat cutting edge is used whereas in case of soft strata the sharp
edged cutting edge is used.
6. Bottom Plug – The bottom plug transmits the load to soil below and
resists uplift forces. The thickness of the plug varies from 0.5 – 1 times
the inner diameter of the well.
7.Sand Filling – Sand filling is the part that lies in between the top and
bottom plug. Its main function is to provide stability to well and reduce
the tensile stress due to the bending moment along with the
distribution of load from the superstructure.

14. 8. Intermediate Plug - Wells resting on clayey strata, it is not preferable
to fill the space inside the well completely with sand. In such cases, sand
filling is not done or sand is filled up to the scour level. A concrete plug
covering the filling is usually provided, known as intermediate plug.
Usually, thickness of intermediate plug is taken as 500 mm.

15. (a) Vertical Loads:
i. Self-weight of well.
ii. Buoyancy
iii. Dead load of superstructure, substructure.
iv. Live load, and
v. Kentledge during sinking operation
(b) Horizontal Forces:
i. Braking and tractive effort of moving vehicles.
ii. Forces on account of resistance of bearings.
iii. Forces on account of water current or waves.
iv. Centrifugal force, if the bridge is situated on a curve.
v. Wind forces or seismic forces.
vi. Earth pressure.
vii. Other horizontal and uplift forces due to provision of transmission line tower (broken
wire condition) etc.

16. As far as possible wells shall be sunk without any tilt and shift. A tilt of 1 in
100 and shift of D/40 subject to a minimum of 150 mm shall be taken into
account in the design of well foundation (D is the width or diameter of well).
If greater tilts and shifts occur, their effects on bearing pressure on soil,
steining stresses, change in span etc. should be examined individually.

17. The depth of well foundation is mainly influenced by two factors:
a) Minimum grip length below the depth of maximum scour
b) Base pressure at permissible limit
The well need to embedded or sunk below the maximum scour level to a required
depth in order that the resistance from the sides of well is able to withstand the
lateral forces acting on the well. The depth of the bottom portion of well from the
scour level is called the grip length. While the selection of depth of foundation we
require to consider the grip length and bearing capacity of soil strata. The
maximum and minimum base pressures during the drastic or critical loading
conditions have to remain under the permissible range.

20. • Length of Bridge : 559.60 Mt.
• Numbers of Piers : 17 Nos. (With Abutments)
• Type of Foundation : Well & Pile Foundation
• Sub- Structure : Pier, Pier Cap
• Super-Structure : RCC Girder & PSC Girder
• Number of Span : 10 Nos. of 40m.span with PSC Girder &; 6 Nos. of 26.60mt. Span
with RCC Girder
• Total Width of Bridge : 15.00 Mt. (With Foot Path)
• Carriage Width of Bridge : 10.50 Mt. (2 Lanes)
PROJECT OBJCTIVE
• For connecting magarwada, moti daman and kachigam, nani daman. For connectivity travelling was done
through vapi-daman road.
• The distance between this two areas is 12 Kms and after the construction of this bridge it will decrease to
just 3 Kms.

28. 1. WELL CAP
3. SAND FILLINF
4(A). CURB
4(B). CUTTING EDGE
5. BOTTOM PLUG
6. SOIL
2(A). TOP PLUG
2(B). STEINING

33. PLAN 1. EXCAVATION OF CIRCULAR
AREA
EDGE CENTRE CENTRELINE
OF ISMB
300
3. HEAVY PCC OF 300 MM
FOUNDATION OF PLATFORM
PCC
2. STONE AND BRICKS FILLED

35. • TESTING OF JOINTS
• In this initially paste of white cement is
cement is applied all over the joints of
joints of well. After drying of it, spraying
spraying of kerosene is done. Due to
Due to which if there is a void there will
there will be bubble formation of cement
of cement coming out. This will give idea
give idea about wherever welding space
welding space is there and must be filled.
must be filled.

40. • For well foundation sinking it is always necessary to know the
high tide and low tide, i.e. height of water. For this the
engineer takes the data of Mumbai online as the data for
daman is just available for one week. So seeing the chart of
Bombay, water level of daman is known as daman is 2hrs
later in water flow. Hence the same tide of almost same
height strikes daman after 2 hrs of its strike in Bombay.
DATA OF WATER LEVEL

45. SINKING
METHDOLOG
Y
CRANE GRABBING AND CHISELING
LABOUR WORKING AND GRABBING
BLASTING AND GRABBING
POCLAIN AND GRABBING USING TWO CRANE
POCLAIN AND GRABING USIG ONE CRANE
DIVERS AND GRABBING

49. 1. WOODEN BLOCKS for creating a
joint.
50 × 100 mm
2. Blocks removed after initial set.
(30 Minutes)
3. SCRATCHING on surface is done
before second layer of concrete.
4. CONSTRUCTION JOINT is created.

51. DEWATERING Initially the dewatering is done of water which has been gathered below
during high tides.
DRILLING OF
ANCHOR BARS
The drilling is done in the hard rock strata using drill for inserting 6 bar of
25 mm dia rebar of 3000mm ht for anchoring of well inorder to hold it
properly . The bars may be anchored in minimum 65Ø boreholes and
grouted.
DEWATERING
(If Required)
If there is time between anchoring and concreting, water may have blowed
in and it is important to do the dewatering.
CONCRETING Concreting (PCC) is done of M15 grade of proportion 1:1.5 Cement mortar
of total height 3150 mm.

54. TRANSFER TO
PONTOON
The crushed sand is transferred on pontoon and the pontoon is then
moved near the well where fiiling will take place.
SAND FILLING The sand is filled in layers of 5 mt. using crane of total height 9.169
mt.
WATER FILL The water is filled in the sand upto 2.5 height of sand filled. Natural
compaction method is used.
COMPACTION For compaction chisel is used.

55. SAND
LEVELLING
The sand is levelled properly to ensure finish surface of top plug.
CURING OF
SAND
Before starting of concreting the curing of sand using water is
dne for proper bonding.
CONCRETING The laying of concrete of grade M25 is done in the top plug of
500 mm height.

58. SURVEYING The leveling and tilt and shift is continously checked in order for proper
alignment of well
REINFORCEME
NT
The rebar of 10 mm and 16 mm diameter are used.Those are
connected in form of links.
FORMWORK The 20 mm M S Plate are used for formwork which are erected by
welding it to rebar and the below steining.
CONCRETE The conrete of grade M35 is transferred from miller to well cap
through the pump and concrete pipes.
CURING The curing is done by wet jute bags and by the method of water filling.
DESHUTTERIN
G
The deshutterinf is done after 14 days.The support with rebars is
chipped of above the concrete surface using gas cutting.