Piles in Construction

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Questions and Answers

What is a major advantage of steel piles?

High resistance to corrosion

Easy to handle during transportation

Large bearing capacity (correct)

Less expensive than other types of piles

What is a disadvantage of steel piles?

High bearing capacity

Easy handling during transportation

Low cost

Corrosion and electrolysis damage (correct)

What is the purpose of a composite pile?

To facilitate the installation of a pile

To reduce the cost of piling work (correct)

To increase the bearing capacity of a pile

To improve the durability of a pile

How do end bearing piles transmit loads?

Through the bottom tips to a firm stratum below Signup and view all the answers

When are friction piles used?

When the hard stratum does not exist at a reasonable depth Signup and view all the answers

What is the conventional method of pile driving?

Applying a force on the pile by letting a weight fall Signup and view all the answers

What restricts the length of a pile?

The mode of transportation available Signup and view all the answers

What is the main advantage of driven piles?

They can penetrate through stiff layers or boulders Signup and view all the answers

What is the purpose of using piles in structures like transmission towers and off shore platforms?

To resist the uplift forces Signup and view all the answers

What type of soil may require the use of piles to transfer the load below the active zone?

Expansive soil Signup and view all the answers

What is the primary reason for using piles in areas where the soil condition is poor?

To prevent washout or erosion of soil Signup and view all the answers

How are piles classified?

According to their material, mode of load transfer, method of installation, and use Signup and view all the answers

What is the maximum load that a timber pile can typically carry?

15 to 25 tons/pile Signup and view all the answers

What is an advantage of using timber piles?

They are economical and suitable for impact absorption Signup and view all the answers

What is a disadvantage of using timber piles?

They are prone to damage by hard driving and have small bearing capacity Signup and view all the answers

What type of concrete piles can be used?

Either pre-cast or cast in-situ piles Signup and view all the answers

What is a crucial consideration for the suitability of driven piles in certain soils?

Poor drainage properties Signup and view all the answers

What is the first step in the construction process of driven cast in-situ concrete piles?

Permanent pile casing is made ready for driving Signup and view all the answers

What is the purpose of using bentonite in bored piles construction?

To stabilize the bore-holes Signup and view all the answers

What is the primary function of the grout pipes in a screw pile?

To inject fluid grout into the surrounding ground Signup and view all the answers

What is the purpose of the temporary casing in bored piles construction?

To stabilize the bore-holes in the upper layer Signup and view all the answers

What determines the length of the temporary casing in bored piles construction?

The actual soil condition encountered on site Signup and view all the answers

What is the primary load that bored piles are designed to resist?

Axial compressive loads Signup and view all the answers

What is the purpose of the rotary drill rigs in bored piles construction?

To perform the pile boring operations Signup and view all the answers

Study Notes

Pile Foundations

Piles are used for foundations of structures like transmission towers and offshore platforms that are subjected to uplift.
Piles are used to transfer the load below the active zone in expansive soils like black cotton soil that swell or shrink with water content changes.
Piles are required when soil conditions are prone to washout, erosion, or scour underneath shallow foundations.

Classification of Piles

Piles are classified according to materials used, mode of load transfer, method of installation, and use.
Materials used: timber, steel, concrete, and composite piles.

Timber Piles

Timber piles are made from tree trunks, trimmed of branches, and designed for a maximum load of 15 to 25 tons/pile.
Additional strength can be obtained by bolting fish plates to the sides.
Timber piles last for about 30 years and are used for structures with moderate loads and temporary structures.
Breadth of timber piles ranges from 12 to 16 inches.

Advantages of Timber Piles

Low cost per running length of the pile.
Suitable for impact absorption due to timber's resilience.
Easy to install and uninstall if necessary.

Disadvantages of Timber Piles

Small bearing capacity.
Untreated timber piles above groundwater may last more than 25 years but are not permanent.
Prone to damage by hard driving.

Concrete Piles

Can be pre-cast or cast in-situ, and are generally reinforced.
Driven cast-in-situ concrete piles are constructed by driving a permanent pile casing, followed by reinforcement and concrete pouring.

Bored Piles

Constructed by boring through overlying soils to find a bedrock strata or remain in the soil to act as shaft friction and end-bearing piles.
Piles are designed to resist axial compressive loads.
Construction involves rotary drill rigs, temporary casing, and bentonite for unstable subsoil conditions.

Screw Piles

Equipped with internal grout pipes extending downwardly through the tubular pile shaft.
Grout pipes connect with side-opening ports in the shaft side wall to inject fluid grout into the surrounding ground.
Pile length is restricted depending on the mode of transportation available.

Steel Piles

Have a large bearing capacity and can penetrate through stiff layers or boulders.
Less soil displacement during driving.
Can withstand rough handling.

Disadvantages of Steel Piles

High possibility of damage from corrosion and electrolysis.
Relatively expensive unless the bearing stratum can develop large pile capacity.
Less effective than friction piles.

Composite Piles

Made by driving two different materials one over the other to achieve economy in piling work.

Mode of Load Transfer

End-bearing piles transmit the load through the bottom tips to a firm stratum below.
Friction piles transfer the load through skin friction between the embedded surface and surrounding soil.

Classification by Method of Installation

Driven piles
Driven and cast-in-situ piles
Bored and cast-in-situ piles
Screw piles
Jacked piles

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Description

This quiz covers the uses of piles in construction, including their application in foundations for structures like transmission towers and offshore platforms, as well as in expansive soils and unstable soil conditions.