Category Archives: piles

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.

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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.

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Piles ..Piling ..everywhere !

Dear Friends ,

Today I plan to take you for a site visit.11

This site is quite near to the river .

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The hard strata at this location is not available till almost 7 Meters and hence PILING was considered as a better  option as compared to OPEN foundations

You shall see the piling work actually taking place here.

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What you are seeing in this picture is the TRIPOD used for the piling which is done by the HAMMERING METHOD.On the right side, you can see the WINCH which pulls the dead weight ( HAMMER ) upto the top of the TRIPOD through a steel wire.

The Hammer gets dropped from a height of 6 m and penetrates the ground.

For the upper most soil which is liable to collapse inside the bore , a casing pipe of about      2 M length is used. After this depth , there is a reasonably soft soil and hence soil does not collapse.

You can see the CASING PIPE in this photograph.

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After doing the boring for about 7.25 M to 7.5 M , hard rock is available.

The hard rock is also cut through CHISELING [ mounted with the dead weight ].

So pile goes inside the hard rock for about 300 mm to 450 mm.

The specimens of soil and rock fragments collected from different depths are properly preserved and tagged with information like Pile no , depth ,time etc.                                            [ This is used for exact analysis of the strata when needed ]

Now the Re-Bar cage is lowered inside the fresh boring .

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You might be interested to know the details of the PILES.

PILE Dia : 500 mm.

REBARS :

Main bars :6 Nos x 20 Ribbed bars of Grade 500.

Rings :

  1. Circular rings 6 Dia. MS @ 200 mm C/C on the inside of cage
  2. Helical rings 6 Dia. MS @ pitch of 200 mm on the outside of cage

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Set of helical rings ready for fixing on the cage.

Following picture shows the drum on which these helical rings are mould.

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This picture shows the stand on which the PILE CAGE is prepared.

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After lowering the REBAR cage , concreting is done for the pile.

It is done with a TREMIE so that concrete can be poured directly at the base of the PILE.

This is important so that segregation of concrete does not take place.

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USE OF TREMIE FOR CONCRETING

Remember : The practice is to cast all PILES which are bored in a day.                                            This is important from :

  1. Safety point of view.
  2. To avoid the risk of soil getting collapsed overnight
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AUTHOR WITH THE ENGINEERS AT SITE.

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THANK YOU SO MUCH ..

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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

 

AUTHOR SHOWING THE PILE REINFORCEMENT  [ NOT YET POSITIONED ] FOR FLYOVER AT PUNE.
AUTHOR SHOWING THE PILE REINFORCEMENT
[ NOT YET POSITIONED ] FOR FLYOVER AT PUNE.
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

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