Well foundations are commonly used for major bridges in India to resist large lateral forces. They are constructed similarly to conventional wells but are more rigid. Different well foundation shapes exist including circular, double D, and rectangular designs. The selection depends on the soil strata. For example, constructing a well foundation in bouldery soil like for the Pasighat Bridge in India was difficult due to large boulders and reduced working periods from heavy rainfall. Pneumatic caisson wells also risked worker health issues from changes in pressure. Proper planning of well construction based on soil data collection is important.

2.  Well foundation is the most commonly adopted
foundation for major bridges in India. Since then many
major bridges across wide rivers have been founded on
wells.
 Well foundation is preferable to pile foundation when
foundation has to resist large lateral forces.

3.  The construction principles of well foundation are similar
to the conventional wells sunk for underground water.
 But relatively rigid and engineering behaviour.

4.  Well foundations have
been used in India for
centuries.
 The famous Taj Mahal at
Agra stands on well
foundation.

5.  To know the construction of well foundation.
 To know the different types and shapes of well
foundations.
 To know which type of well foundation is suitable for
different types of soil strata.

6.  Wells have different shapes and accordingly
they are named as:-
1. Circular well,
2. Double D well,
3. Twin circular well,
4. Double octagonal well,
5. Rectangular well.

7.  .

8. Well
Open caisson
or well
Box Caisson
Pneumatic
Caisson

9.  Open caisson or well: The top and bottom of the caisson is open
during construction. It may have any shape in plan.
 Box caisson: It is open at the top but closed at the bottom.
 Pneumatic caisson: It has a working chamber at the bottom of the
caisson which is kept dry by forcing out water under pressure, thus
permitting excavation under dry conditions.

14.  .

16. Well foundation construction in bouldery
bed strata

17. Andhra Pradesh
Pasighat Bridge

18. The Important Factors of the bridge were as follows..
 Length of the bridge - 704 mts.
 Foundation:-
i. Type -Circular Well.
ii. Outer Diameter -11.7 mtrs.
iii. Inner Dia. -6.64 mtrs
iv. Steining thickness -2.53 mtrs.
v. Well curb height -4.5 mtrs.
vi. Angle of cutting edge -33 degrees.
vii. Grade for steining concrte -M25

19. Boulder dredged during well sinking
Pasighat Bridge

20.  The construction in flowing water was carried out by
means of heavy machinery like dozers , dump trucks
and excavators , etc.
 Pneumatic sinking and conventional sinking method is
adopted for construction purpose.
 Sand was taken from the river and cleaned before
transportation and then is used as sand filling.

21. 1. The sinking of the well becames very
difficult due to the presence of large size of
boulders in the strata.
2. Basically there were difficulties in finally
deciding the foundation level on such
strata.
3. Due to heavy rainfall in the area a
considrably reduced working period was
available in the region.

22.  In case of sinking process of pneumatic caisson ,
workers under pressure may suffer from
“Decompression sickness”(Caisson disease).due to
rapid change in pressure.
 Construction of the Brooklyn Bridge, which was built with
the help of caissons, resulted in numerous workers
being either killed or permanently injured by caisson
disease during its construction, including the designer's
son and Chief Engineer of the project.

24.  Construction of a well foundation in bouldery bed strata
calls for a dedicated effort on the part of the executives.
 The data of the soil strata encountered at the site must
be kept in detail for each meter and if required a review
of the foundation must be carried out , based on actual
soil parameters obtained during sinking.

25.  M.N Som. , S.C Das , Theory and practice of foundation
design , Ashok.k.Ghosh,New Delhi,2006.
 P.C.Varghese,Foundation Engineering,
Ashok.k.Ghosh,New Delhi,2005.
 Bowles, J.E. ,Foundation Analysis And Design(International
Student Edition) ,Mc-Greww hill,Singapore,1988.
 Saha G.P. “Analysis and Design of Varanasi Bridge
Well Foundations – A Conceptual Approach” Journal
of Indian Roads Congress Vol. 54-2. Paper
presented in the Annual Session of IRC in November
1993.

26.  Dhiman.R.K. , “Well foundation construction in bouldery bed -
A case study” international association of bridges and
structural engineers (IABSE),Punjab,1999.
 Dr.Priti Maheshwari , “NPTEL”,IIT Roorkee , http://nptel.ac.in
 Dr.Kousik.Deb,“Myopencoures”,IIT
Kharaghpur,http://myopencourses.com/video/well-foundation
 Wikipedia,http://en.wikipedia.org/wiki/Caisson.

27. Thank youThank youThank you