Concrete Foundation Work (part 02)

Concrete Foundation Work in Building Construction (part 02)

First of all read (part 01)...

>> Concrete Foundation Work in Building Construction (part 01)

Deep Foundation

Types of Deep Foundation

The types of deep foundations in general use are as follows,

1. Basements
2. Buoyancy rafts (hollow box foundations)
3. Caissons
4. Cylinders
5. Shaft foundations
6. Pile foundations

Deep Foundation can be divided mainly three part,

↬ Pile

↬ Well

↬ Casing

Pile Foundation

Where the sub soil has poor or uncertain bearing capacity and which contains shrinkable Clay or the foundation is deeper than 3m, its often economical to use pile foundation.

Definition of pile,

A pile is a column of reinforced concrete, steel, wooden either cast in-situ or driven in to the ground (pre cast concrete pile) to transfer load through the poor bearing soil.

pile foundation is designed in such a way that the load from the structure.

Pile foundation is designed in such a way that the load of the structure to transmit to the sub soil without any failure.

Pile foundation used in…

> The sub soil having poor bearing capacity.

> When the structure is massive with heavy reinforcement.

> In the marshy lands

> In case of bridges.

> River or any water structure in near by area.

Well (What is a Well Foundation?)

Well foundation is a type of deep foundation which is generally provided below the water level for bridges. Cassions or well have been in use for foundations of bridges and other structures since Roman and Mughal periods.

The term ‘cassion’ is derived from the French word caisse which means box or chest. Hence cassion means a box like structure, round or rectangular, which is sunk from the surface of either land or water to some desired depth.

Caisson (What is a caisson?)

A caisson foundation also called as pier foundation is a watertight retaining structure used as a bridge pier, in the construction of a concrete dam, or for the repair of ships. It is a prefabricated hollow box or cylinder sunk into the ground to some desired depth and then filled with concrete thus forming a foundation.

Caisson foundation is Most often used in the construction of bridge piers & other structures that require foundation beneath rivers & other bodies of water. This is because caissons can be floated to the job site and sunk into place.

What is casing in pile foundation? (Casing Pipe)

Basic reason of providing the casing pipe is to prevent the soft soil from falling into the pile bore.
If the casing pipe is not provided , the clay or the soft soil shall keep on falling in the excavated bore of the pile and while casting the concrete, this shall get inadvertently mixed in the cement concrete.

In Cast in-Situ there are 2 types of Casings

1. Temporary casing :- It is a type of casing which is removed after the casting of concrete is complete, typically before start of final setting. As you must be well aware, the loose soil is generally found in the Initial layers of the Bore. So, in case of a temporary casing the casing is not much deep. If we have a deep temporary casing, it is very difficult to remove after completion of casting.
2. Permanent Casing :- It is a type of casing which is concreted with the concrete and remains there for Life of the Pile. The general practice is placing the casing before pouring the concrete so that no soil gets accidentally mixed with the concrete. These kind of casings are seen where the soil is very loose/fine & the chances of caving of the pile is more.

Displacement Piles

Displacement piles are usually created using steel, concrete (pre cast) or timber which are driven or screwed into the ground to displace the soil.

The piles or forming tube is driven into the required depth which is a measure of the sub soil.

To driven pile to the earth, it’s number of hammer blows may obtained.(figure 1*)

figure 1* . (how to driven to earth displacement pile)

Timber Piles

These piles are used for shallow depths.

For example:- river banks, water lodge areas.

Preformed (pre-cast) concrete piles variety of types available. these percussion driven using a drop or angle acting hammer.

H-Section

Steel piles

Standard steel sheet pile are mainly used for marine structure.

Sheet piles

Sheet pile walls are retaining systems are mainly used for deep excavations. the full wall is formed by connecting the joints of adjacent sheet pile section.

steel sheet piles are the most common material, because of several advantages over than other materials.

> Provides high resistance to driving stress.

> Light weight.

> Can be re use on several projects.

> Having long service life.

> Easy to adopt the pile length by welding.


Sheet Pile Walls are Constructed By...

1. Sequence of sheet pile section and ensuring that the sheet pile has interlocking system.

2. Driving the individual sheet pile to the required depth.

3. Driving the second sheet pile with the interlocks between the first sheet pile and the second locked.

4. Repart step 2 to 3 until the wall is finished.

Disadvantage of Sheet Piling

1. Section can rarely used as part of the structure.

2. Difficult to reach to required depth.

3. Settlement of adjacent properties may take place due to vibrations.

Replacement Pile

These are called bored piles also. They are used for primarily in the cohesive soil. In construction time it’s noise and vibration is limited.

Replacement piles are three types...

⇉ Percussion piles

⇉ Flush bored piles

⇉ Rotary piles

Percussion pile

They formed as a pressure piles. Used for small and medium project. 

Flush bored pile

Using large projects. 

Rotary bored pile

Small diameter rotary bored piles are Used for a small projects. light loads can bear. 

Large diameter rotary bored piles are used for large projects.

Pile caps

Pile can be used for simply to support loads. so its more economical the pile caps link together with reinforced concrete beam.

look at the following figure...

Advantages and Disadvantages of Displacement and Replacement piles.

Advantage of Displacement pile...

➛ The equipment and installation methods are time-tested and well proven.

➛ Advances in materials, equipment, methods, and testing continually combine to improve the efficiency of driven piles.

➛ Driven piles require no curing time.

➛ can be driven in natural sequence rather than skipping alternate piles, thus minimizing the moving of the equipment and speeding installation.

➛ A driven pile is a tested pile

➛ Driven piles can be easily fabricated or specified for high structural strength,

➛ Construction operation not affect by ground water

➛ Soil disposal is not necessary.

Disadvantage of Displacement pile

↯ Not easy to transport.
↯ Not easy to handle.
↯ Cant use for deepest foundations.
↯ Pile length and the diameter of pile is limited.
↯ May break during driving.
↯ Noise and vibration problems may occur.
↯ Cannot driven in condition of low head room.

Advantages of Replacement piles

* Less noise and less vibration problems

* Equipment can break up practically all kinds of obstruction

* Can be installed in conditions of low headroom

* Depth and diameter can be varied easily

* No ground heave

Disadvantages of Replacement piles

⇝ Concrete cannot be inspected after installation.

⇝ Liable to squeezing or necking.

⇝ Drilling a number of piles may effect to adjacent buildings.

⇝ Cannot be extended above ground level without special adaption.

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