What is Sheet Piling?

Sheet piling can be used for various construction and civil engineering projects including building foundations, retaining walls and underground structures such as car parks, pump houses and basements. Other applications include marine structures such as cofferdams, seawalls and canals.

Permanent retaining walls utilising sheet piles are used on schemes large and small, from simple projects to complex slope stabilisation solutions. They may be designed to both retain temporary excavations and to act as the permanent retaining structure, often in conjunction with the base slab which offers propping to the wall.

Sheet pile walls are also commonly used in service yards of commercial and retail sector developments, flood defence schemes, bridge abutments and boundary walls.

The different types of sheet piles include:

• Wooden sheet piles
• Wakefield piles
• Steel sheet piles
• Precast concrete sheet piles
• Light-gauge aluminium sheet piles
• Vinyl sheet piles
• Fibreglass sheet piles
• Cantilever sheet piles

Cantilever sheet piles are walls that do not have any supports and thus have a free, unsupported excavation. Cantilever walls restrain retained earth by the passive resistance provided by the soil below the excavation.

Before installation, the ground is inspected for stability and the sheet piles are inspected for cracks or any other damage. Traditionally, sheet piles are driven or hammered into the ground using a vibratory hammer or an impact hammer, if the ground is too hard or dense. However, these methods produce high frequencies of noise and vibration.

For areas or sites that require lower levels of noise or vibration, sheet piles can be installed using a silent press, which is noise and vibration-free. The pile press equipment essentially ‘walks’ along the pile heads, using a self-moving system. This means no crane support is required to move the pile press along the line of the wall, allowing its employment in locations traditionally difficult to reach, such as by water.

This video demonstrates the installation of pressed sheet piles using a hydraulically-powered static load press-in method:

For difficult soil conditions that contain larger particles, driving assistance may need to be considered. One example of driving assistance is water jetting. A high-powered water jet is attached at the toe of the sheet pile and uses low pressure to push the particles out of the way, allowing the pile to be easily inserted into the ground.

A sealing system provides a cost-effective solution to control water seepage through the wall, for instance, to minimise the risk of settlement of adjacent property or keep excavations dry.

The water tightness of ArcelorMittal or Larssen interlocks invariably improves with time, but a sealant provides a means by which the flow of water can be controlled faster and more reliably.

The water flow through sealed interlocks can be calculated with a practical design method backed up by several in-situ full-scale tests.

Each construction project is unique because of ground conditions, water tightness requirements, installation methods and vary from site to site. Therefore, the choice of a sealing system must be made carefully considering all the specific constraints and requirements.

The integrity of a sealant will depend upon its suitability regarding the installation and the driving method, as well as the soil and water conditions.

The disadvantages of sheet piling include:

• In rocky soils and have challenging conditions, such as large boulders, sheet piles rarely can be driven to the desired depth.
• Sheet piling typically requires heavy equipment to install.
• If not installed and handled carefully, sheet piles will deviate relatively quickly during driving.

There are a number of alternative retaining wall solutions. King Post Walls, for example, are a cheaper alternative to sheet piling if concrete infill panels are chosen.