All you need to know about sheet piling

[edit] Introduction

Sheet Piling is used to provide temporary and permanent walls in the construction industry. Sheet piling is used as excavation support and for soil retention. It creates a border which keeps the soil back, away from the structure.

[edit] Technical details

Sheet piles are designed to interlock with each other. They are installed in sequence along the planned excavation perimeter. When arranged together, they form a wall for permanent or temporary earth support, along with anchors to provide extra lateral support.

Permanent sheet piles are designed to provide a long service life; installed with the help of vibratory hammers. If the soil is too dense or hard, impact hammers are used. Depending on the condition of the site, the sheet piles can be hydraulically pushed into the ground.

They can be made of recycled steel, and can be reused for other purposes; making them a sustainable option.

[edit] How sheet piling works

Usually, the material used to make piling sheets is steel, but wood and vinyl sheets are also used at times. The concept is to design narrow, interlocking sheets that can be connected and driven into the ground to form a wall. Stability and strength are defined by the shape and material of the sheets. Steel is considered to be the most appropriate material if the requirement is to withstand large bending forces and pressure.

[edit] Uses of sheet piling

When construction is taking place in a confined space, then temporary walls are used to prevent cave-ins; offering protection to the workers working in the vicinity of the area.
In a home environment, sheet piling is used as permanent walls as they provide stability and durability to the interior walls (especially basement walls).
Pilling is also used to prevent floods to structures close to shorelines.
To protect foundations from water damage.
To support excavations for parking structures, basements, foundations, pump houses, and to construct cofferdams, seawalls and bulkheads.

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Types of sheet piling =

[edit] Anchored sheet piles

Anchoring the sheet piles causes less penetration, which is economical when the height is less than 6m. This is because the anchor walls are pre-stressed to remove the slack from the system. It remains as it is until creep occurs. Anchor walls provide better back-slope subsidence because they undergo less lateral deflection. There are two major reasons for subsidence:

If the anchor holes cave before grouting.
If the cohesion material flows into the excavation through the opening which was earlier made for anchor installation.

The anchors create a large gravity wall by holding the soil mass between the anchors and the wall in compression.

[edit] Cantilever sheet piles

These are usually used for heights of 6m or less. In geotechnical practices, cantilever embedded retaining structures are used as sheet walls for temporary retaining structures and diaphragms & pile walls as permanent retaining structures.

[edit] Cofferdams

When a bridge is being built, cofferdams can be used as a temporary structure designed to keep soil and water out of the excavation. It provides a dry work environment underwater by sealing the structure with concrete to prevent water from seeping in.

[edit] Advantages of sheet piling

Advantages of sheet piling include:

It is light in weight, making it easy to lift and handle.
It is recyclable and reusable.
The pile length and design are easily adaptable.
Joints are designed to withstand the high-pressure required to drive them into place.
It requires only a little maintenance above and underwater.

[edit] Disadvantages of sheet piling

Disadvantages include:

If the soil is rocky or has large boulders, it becomes difficult to installs sheets into it.
If you are going to use vibratory hammers or impact hammers to install the sheets into the ground, this can cause neighbourhood disturbance.
Most of the sheets are used as temporary structures. After the project is completed, the sheets are removed, which can be costly.

[edit] The basic construction steps

Arrange the sheets in sections to check if the piles will interlock correctly or not.
Hammer the first sheet to the defined depth as per the design.
Use vibratory hammers for installation, but use impact hammers if the soil is hard or dense.
Use hydraulics to push the sheets into place if vibrations are prohibited at that particular site.
After the first sheet is placed, drive the second sheet so that it interlocks with the first one.
Repeat the process until the wall is completed.
Use connector elements to maintain the integrity of the wall if it requires complex shapes.