What is a Sheet Piling / Shoring

Sheet piling and shoring are temporary structural techniques used during excavation works to support the sides of trenches, pits or other excavated areas. These methods are essential in construction and civil engineering to prevent the collapse of soil or surrounding structures into an open excavation. By providing lateral support, they help create a safe working environment for personnel and protect adjacent utilities, roadways, or buildings.

Although the terms are often used interchangeably, they refer to slightly different systems. Sheet piling typically involves the use of interlocking steel or vinyl sheets driven vertically into the ground to form a continuous barrier. Shoring, on the other hand, encompasses a broader range of support systems, including timber, hydraulic or mechanical braces and panels.

Both systems are crucial in temporary works design, especially where deep excavations, unstable soil conditions, or nearby structures increase the risk of ground movement.

The Purpose of Shoring and Sheet Piling

The main objective of sheet piling and shoring is to ensure the stability of an excavation and the safety of workers operating within or near it. Without adequate support, the sides of a trench or pit can collapse due to the pressure exerted by the surrounding soil, groundwater or structural loads.

The functions of sheet piling and shoring include:

  • Preventing soil collapse into the excavation

  • Maintaining the integrity of nearby structures or roads

  • Reducing ground movement and subsidence

  • Controlling groundwater ingress

  • Allowing construction to proceed safely in confined or urban sites

These systems are particularly important in sewer construction, basement installations, foundation works, and the installation of underground utilities such as water, gas and drainage pipes.

Common Types of Shoring Systems

Shoring encompasses a range of temporary support methods. The choice of system depends on soil type, depth of excavation, water table level, available space and duration of works.

1. Hydraulic Shoring

Hydraulic shores use pre-engineered aluminium or steel supports with hydraulic pistons that apply outward pressure to support trench walls. This method is quick to install and remove and is often used in linear trenches for pipe laying.

2. Timber Shoring

Traditional timber shoring involves wooden uprights, walers and struts that are manually placed within the excavation. Though labour-intensive, it is still used for small-scale projects or in historic areas where mechanical equipment cannot operate.

3. Soldier Piles and Lagging

This method uses vertical steel H-piles (soldiers) driven at regular intervals along the excavation perimeter. Timber planks (lagging) are then inserted between the piles as the excavation progresses. This system is ideal for deep and narrow excavations.

4. Trench Boxes (Drag Boxes)

Trench boxes consist of two steel panels held apart by struts or spreaders. They are designed to be placed in open trenches and protect workers while installation progresses within the protected zone. This method does not support the excavation fully but provides safe access.

Understanding Sheet Piling

Sheet piling involves driving interlocking sheets into the ground to create a continuous wall. These sheets are typically made from steel but can also be formed from vinyl, wood or composites depending on the site conditions and environmental requirements.

Key Characteristics

  • Sheets interlock using a tongue-and-groove system to form a watertight or semi-watertight barrier

  • They can be installed using vibration, pressing or impact driving techniques

  • Sheets are reusable and suitable for multiple projects

  • Sheet piles can be used both temporarily and permanently, depending on the design

Sheet piling is particularly effective in urban environments where ground movement must be minimised, or where excavation is required below the water table.

Applications of Shoring and Sheet Piling

Both systems are widely used in the construction and infrastructure sectors. Typical applications include:

  • Excavation for deep basements or underground car parks

  • Installation of underground utility networks (e.g., sewerage, water, gas)

  • Support of cofferdams for bridge piers or waterfront structures

  • Trench excavation in urban or congested environments

  • Soil retention next to roads, railways or buildings

  • Retaining walls in temporary or permanent earthworks

In sewerage and drainage works, shoring and sheet piling are often necessary to provide safe access to deep manholes, culverts or connection points while preventing collapse of the surrounding soil.

Design Considerations

When selecting a sheet piling or shoring system, engineers must evaluate several factors to ensure that the chosen solution is safe, cost-effective and appropriate for the conditions.

Key considerations include:

  • Soil type and properties: Cohesive soils behave differently from granular ones and may require different support pressures.

  • Water table level: Excavations below the water table may need dewatering systems or watertight sheet piles.

  • Depth and size of excavation: Deeper excavations require more robust systems with higher load-bearing capacity.

  • Proximity to other structures: Nearby buildings, roads or services may influence the choice of method and installation technique.

  • Duration of works: Temporary works for short-term projects may justify lighter systems, while long-term or permanent use requires more durable materials.

  • Environmental impact: Vibration-sensitive areas or contaminated ground may dictate non-intrusive methods or specialised materials.

The design must comply with the Construction (Design and Management) Regulations (CDM) and be supported by structural calculations and a safe method of work.

Installation and Removal

The process of installing sheet piling or shoring varies depending on the chosen system, equipment availability and site constraints. General steps include:

  1. Site preparation and survey

  2. Delivery and positioning of materials

  3. Driving or pressing sheet piles, or assembling shoring frames

  4. Excavating in stages while installing support as excavation progresses

  5. Monitoring ground movement and adjusting supports if needed

Removal is often the reverse of installation. In some cases, sheet piles may be left in place as part of the permanent structure, particularly in waterfront or retaining wall applications.

Modern construction practice increasingly incorporates trenchless or low-impact methods to reduce noise, vibration and disruption during installation.

Health and Safety Considerations

Excavation works, particularly in unsupported trenches, are among the highest-risk activities on a construction site. The use of properly designed and installed shoring or sheet piling systems is a critical control measure.

Key safety requirements include:

  • Never entering an unsupported trench or excavation

  • Installing support systems in advance of excavation

  • Monitoring for signs of ground movement, settlement or instability

  • Ensuring equipment is installed and removed by competent personnel

  • Following manufacturer’s guidance and approved safe systems of work

  • Considering confined space entry procedures if working in deep or enclosed excavations

Accidents involving trench collapse can result in serious injury or fatalities, making adherence to best practice and regulation non-negotiable.

Regulation and Standards

In the UK, excavation support systems must comply with relevant health and safety legislation and design codes. These include:

  • The Health and Safety at Work Act 1974

  • The Construction (Design and Management) Regulations 2015

  • BS EN 1997-1 (Eurocode 7): Geotechnical design

  • Temporary Works Forum guidance: Best practices for design, installation and removal of temporary works

Temporary works designs must be prepared by qualified engineers and independently checked before use. Risk assessments and method statements are essential for all shoring activities.

Advantages and Limitations

While sheet piling and shoring are highly effective, each system comes with advantages and limitations.

Advantages

  • Allows safe access to deep or unstable excavations

  • Prevents soil collapse and protects surrounding assets

  • Reduces groundwater ingress

  • Flexible and adaptable to site conditions

  • Many systems are reusable and cost-effective over time

Limitations

  • Installation can be noisy or disruptive

  • Vibration from pile driving may affect nearby structures

  • Requires specialist equipment and trained personnel

  • Not always suitable for very hard or rocky ground

  • May require dewatering in high water table areas

Engineers must weigh these factors when planning excavation works and selecting the most appropriate solution.

Conclusion

Sheet piling and shoring are indispensable methods in modern construction, providing essential safety and stability during excavation works. Whether installing a sewer, building a basement or constructing foundations, temporary support systems help manage ground pressure, reduce risk and facilitate efficient project execution. With proper planning, design and installation, these techniques enable safe and sustainable excavation in even the most challenging environments.