1. Well Foundations
Dr.K.V.Krishna Reddy

4. Classification based on Construction methodology

5. Classification based on Shape

7. BED LEVEL
HARD STRATUM

8. Steps in construction of open foundation

10. 2

11. 3. Steining not more than 1. 5m is cast to ensure the well is
3. Steining not more than 1.5m is cast to ensure the well is floating due to buoyancy and the top surface is always above water level
4. The process is continued till the curb rests on river bed
5. Once river bed is reached, excavation is carried out using cranes positioned on pontoons. Not more than 1 to 2m is excavated at a time.
6. As the well sinks under self weight, further Steining is cast.
7. If required kentledge load is provided to expedite sinking process

12. Once
desired depth
is formed 8. 9.

13. ballast, dry conc Gravel, etc…..
It does not penetrate through the soil, but rests on leveled river / canal bed . A concrete cap is provided at the top and riprap is provided at the bottom all round to protect from scour
Grounded by

14. When the velocity of flow is less than 6m/s.
BED LEVEL OF CANAL /RIVER
Floating or Box Caissons are used where the flow of water is less..i.e..
When the velocity of flow is less than 6m/s.
When low volumes of traffic like bullock carts, tractors, men and materials are to be moved across a canal or river tributary.

15. They are used in case of soft soils, running soils where the caisson just caves in before sinking
These are also found useful when hard strata is encountered in the process to reach the desired depth where blasting is required
pressure

17. Misc Equipment

18. movement of men and excavated material.

19. top
Water level

20. Reversed when men come back
compression
and decompression is done slowly to prevent fatal accidents. The Maximum depth of sinking is limited to 35m to 40m as humans cannot bear pressure more than 400kN/sq.m. Men are not allowed to work for more than 2 hours at a stretch. Fresh air is circulated at regular intervals

21. Greater pressure for prolonged time may result in Caisson sickness / Caisson disease, which is a nerve disorder

22. Experienced workmen required
Accident prone
Caisson’s Disease
Bearing capacity can be determined
Well suited for soft and running soils

27. Component design parameters

31. Well cap is designed as a slab considering that the load from the top in the form of a cone with an apex angle of 60 degrees is carried by this and the rest is transfered to the Steining

32. PROBLEMS IN WELL SINKING
Tilts
Shifts
Obstructions during sinking
Wave action during sinking
Impact forces due to equipment during sinking

34. Corrections for tilts