# FOUNDATIONS…beginners guide

Dear Friends ,

Good evening !

The design and selection of a particular type of foundation is a work of the RCC consultant The construction person must know the background so that the interaction with the designer is easy. Read this article so that you know the basics.

# HOW TO DESIGN FRICTION PILES ?

Dear Friends ,

Good afternoon.

Today we shall have a look at the primary considerations for calculating the basic parameters of a friction pile.

But before we take up the discussions , let us have a look at this picture :

Now ,a look at the Friction piles :

Whenever, the depth of the hard strata is so deep that boring up to that depth is either not economical or it takes too much time , it is suggested to go for Friction Piles.

The load is carried by the friction developed between the concrete surface and the surrounding soil

Now let us study the basic guiding calculations :

To illustrate this point , let us solve a few examples :

Another example :

Before making a sketch of the Pile cap , have  a look at this conceptual diagram :

Now we can make a tentative diagram :

# HOW TO FIND CUTTING LENGTH OF CIRCULAR RINGS ?

Dear Friends ,

Good evening !

This is a great query from our friend :

Let us handle the first part of the query in this article.

Here is an example on a circular pile which shall demonstrate the case.

Hope this is quite clear now.

# PILE FOUNDATION : WEIGHT OF REBARS

Dear Friends ,

Good evening.

In the previous article, we found out the REBAR weight of a Pile foundation.

Look here for quick access : PILE : RE_BARS.

Today we also learn how to find out the development length of the main bars if it is not given in the drawing.

# SIMPLE EXAMPLES ON PILE FOUNDATIONS

Let us spend some time on the Pile foundations today.

# How much material is needed per pile ?

Background :

As a construction person , you should also be able to calculate the material required for the construction . Today , we shall learn how to calculate the materials required for the Pile foundations.

Data :

Pile Shape :  Circular

Pile Diameter :  600 mm

Pile Depth : 8.35 M.

Mix of concrete : M20

Reinforcement: 6 HYSD bars of 16mm diameter .

Stirrups :  8 mm diameter bars provided at a spacing of 200 mm C/C [ Center to Center ]

As a construction person , we know the following :

1.Unit weight of  16mm dia HYSD bars : 1.58 Kg/m

2.Unit weight of  8mm dia HYSD bars : 0.39 Kg/m

3.Cover for Pile reinforcement : 50 mm

4.Material consumption for Concrete M20 :

1. Cement : 7.87 Bags/ CuM
2. Sand : 0.41 CuM.
3. Aggregate : 0.83 CuM.

4.Formula for volume of the cylinder = (0.785).D2.H                                                                                     where D : Pile diameter in M & H : Pile height in M.

Having thus prepared , we shall now go for the actual calculations as follows .

Part A : REINFORCEMENT :

A.01 : Longitudinal bars :

Cutting Length of bar : 8350 –( 50+50 ) = 8250 mm = 8.25 M.

Weight :

6 Nos X 8.25 m X 1.58 Kg/m =   78.21 Kg.

A.02 : Stirrups :

Stirrup diameter : 600 –( 50+50 ) = 500 mm.

Cutting length :  ( 3.14) D +( 2x10d )

D : Stirrup  Diameter =500 mm

d:  Diameter of bar used for stirrup = 8 mm.

=  (3.14 x 500 )+( 2x 10×8)  =  1730 mm =   1.73 M.

No of stirrups : ( 8350 / 200 )+1 =  43 Nos

Weight :  43 Nos x 1.73M x 0.39 Kg/m = 29 Kg.

Summary of Reinforcement :

16mm dia HYSD bars : 78 Kg / Pile

8mm dia HYSD bars :   29 Kg / Pile

Part B : M20 Concrete :

Volume of pile :

(0.785).D2.H

=0.785 x 0.6 x 0.6 x 8.35

=2.36 CuM /Pile

Cement required :

2.36 x 7.87 bags = 18.57 bags

Sand Required :

2.36x 0.41 CuM = 0.968 CuM.

Aggregate  Required :

2.36x 0.83 CuM = 1.96 CuM.

Final Summary :

Material required per pile of 600 mm dia. having a length of 8.35 M.

Cement : 19 bags

Sand : 1 CuM

Aggregate : 2 CuM

Reinforcement bars :

16mm dia HYSD bars : 78 Kg

8mm dia HYSD bars :   29 Kg

# What’s the difference between foundation and footing?

Foundations are broadly classified as :

1. Shallow Foundations
2. Deep Foundations

According to Karl von Terzaghi, a foundation is shallow if its depth is equal to or less than its width. Foundations constructed by open excavation are also called shallow foundations.

The term footing is used in conjunction with shallow foundations commonly. A footing is a foundation unit constructed in brick work, masonry or concrete under the base of a wall or a column for the purpose of distributing the load over a large area. A footing or a shallow foundation is placed immediately below the lowest part of the Superstructure supported by it.
Some examples of footings are:

• Combined footings for columns and walls
• Strap footing

The Deep foundations are simply called foundations. The depth of the foundation is more than the width. Some examples are:

• Pile foundation
• Stages in forming vibro-expanded piles
• Well foundation
• Coffer dams

The two terms are also defined as : ‘A foundation is the part of the structure which is in direct contact with the ground to which the loads are transmitted, while the lowermost portion of the foundation which is in direct contact with the sub-soil is called the footing.’

Hope this helps.
Thanks for the A2A Abhinand Ab!

What’s the difference between foundation and footing?