Week 8 Challenge

Aim - For to design a safe capable foundation of bridge it is verry necessary to know the loads on group of pile. And in this challange we have to calculate loads as per IRC 6 for given bridge drawing.

A pile bridge foundation is a structure that uses long poles (referred to as piles), which are made of wood, concrete or steel and which are hammered or bored cast into the soft soils beneath the bridge until the end of the pile reaches a hard layer of compacted soil or rock or gets sufficient skin friction to carry the load.

When the load is more than capacity of one pile, group of piles are used. These piles are joined with pile cap to act as one.

Different loads are

1. Dead load (Due to self weight of superstructure, substructure, foundation and soil weight)

2. Superimposed Dead load (SIDL) excluding wearing course due to crash barrier.

3. Superimposed Dead load (SIDL) due to wearing course.

4. Carriageway live load

a 1Lane of 70R Wheeled

b 1Lane of class A

c 3Lane of class A

d 1Lane of 70R Wheeled + 1lane of class A

5. Wind load

6. Tempreture load

In this challange wind load and tempreture load suggested to ignore.

Components of well foundation.
1. Well Cap
2. Top plug
3. Stening

4. Intermidiate plug
5. Bottom plug
6. Well kerb
7. Cutting edge
8. Filling inside ( Sand / Water )
1) Well Cap.
Well cap is an RCC two way slab structure that is located below the pier/ abutment and above the
well, The well cap contributes the required surface for positioning the pier or abutment and
transfers its loads safely to the well foundation.
2) Top plug
It is a PCC filling which is filled above the sand filling which is located inside the well
foundation it is 300 mm thick above the sand filling.

When well is kept empty it is either not used or made of Reinforced concrete.
3) Stening
Wall of the well foundation is called as stening it is made up of RCC.
For minimum concrete used it is necessary to keep the thickness of steining under control. Thickness is determined based on the following considerations:
It should not be extremely thick so that unnecessary resistance is avoided during
the sinking of the well.
It should not be extremely thin so that it gets destroyed either during the sinking of the well
or under design loads. The stresses generated in the steining should be within permissible
limits under design loads.
The steining should resist the more stresses generated when corrective measures are
taken for tilting and shifting of the well.
Finite element method is used to design the well foundation.
4) Bottom plug
After successful sinking is done then we have to provide PCC fill at the bottom level in the
well foundation bottom plug increase the bearing resistance and gives long term stability
to well foundation.
cement content is use in bottom plug is 330 kg/m3 and provide thickness as 300 mm.
5) Well Kerb.
Well curb is loacated below the stening which is use to transfer all the load from top to the
soil throught the cutting edge while sinking.
It is made up of RCC. and integral angle should be kept in between 30 to 37 degree. and
grade of concrete is use M25. with 72 kg/cm reinforcement.
6) Cutting Edge.
The lowest part of the well foundation is cutting edge and it enables penetration of the
bottom of the well during the sinking.The thickness of the cutting edge and the slope angle
of the inside edge should be such that it should be sharp sufficiently for easy sinking, and
at a similar time should not break when penetrating through the hard rock or soil.
7) Filling
After completion construction of well foundation we have to fill filling insing the foundation
to give stability to the structure it is either sand or water.

8) Filling makes well heavier and gives extra weight. Intermidiate plug is provided at scour level to reduce the filling weight by shortening height.

Sketch of Well Foundation:

Thank you.