Excavation Site Stability  

This week, we have created a go-to guide to prevent a few of the main hazards associated with excavation sites.

Every year people are killed or seriously injured due to collapses or falling materials while working on excavation sites. Workers are at risk from excavations collapsing and burying or injuring them, material falling from the sides into an excavation, and workers or plant equipment falling into excavations.

Excavation sites are not as stable as you may think. It is vital to bear in mind:

  • No ground can be relied upon to stand unsupported in all circumstances.
  • One cubic meter of soil can weigh as much as one tonne.
What You Need to Do

Precautions must be made to prevent the danger to workers in or near excavations. To maintain the required precautions, a competent person must inspect excavation supports or battering at the start of the working shift and at other specified times, ensuring no work takes place until the excavation site is safe.

Commercial clients must provide certain information to contractors before work begins. This should include relevant information on the ground conditions, underground structures or water courses, and the location of existing services.

Additionally, trench-less techniques should always be considered at the design stage, as they replace the need for major excavations. Underground and overhead services may also present a fire, explosion, electrical or other hazard and will need to be assessed and managed.

All of this information should be used during the planning and preparation stage of excavation work. The following provides model ways to prevent a few of the main hazards associated with excavating.

Collapse of Excavations
  • Temporary support – Before digging any trench pit, tunnel or other excavations, decide what temporary support will be required and plan the precautions that will be taken. Make sure the equipment and precautions needed (trench sheets, props, baulks, etc.) are available on-site before work starts.
  • Battering the excavation sides – Battering the excavation sides to a safe angle of repose may also make the excavation safer. In granular soils, the angle of slope should be less than the natural angle of repose of the material being excavated. In wet ground, a considerably flatter slope will be required.
Falling of Dislodging Material
  • Loose materials – Implement controls, such as edge protection, to stop loose materials from spoil heaps from falling into the excavation. Edge protection should include toe boards or other means, such as projecting trench sheets or box sides for protection against falling materials. Head protection should be worn at all times whilst on site.
  • Undermining other structures – Check that excavations do not undermine scaffold footings, buried services or the foundations of nearby buildings or walls. Decide if extra support for the structure is needed before you start. Surveying the foundations and seeking the advice of a structural engineer may be required.
  • Effect of plant and vehicles – Do not park plant and vehicles close to the sides of excavations. The extra weight can prompt the sides of excavations to collapse.
Falling into Excavations
  • Prevent people from falling – Edges of excavations should be protected with substantial barriers where workers are liable to fall. To achieve this, use:

– Guard rails and toe boards inserted into the ground directly next to the supported excavation side or fabricated guard rail assemblies that connect to the sides of the trench box.

– The support system, e.g., using trench box extensions or trench sheets longer than the trench depth.

General Best Practices

By following these essential health and safety tips, you are taking necessary steps towards protecting workers on your construction site. The following tips summarise actions for straightforward excavations, for example, pipe and cable laying, manhole construction, shallow foundations, and small retaining walls.

If your excavation is more complicated, speak to an expert such as a structural engineer.

  • Support the excavation as you go along.
  • Prevent workers and materials from falling in by using strong barriers that won’t collapse if someone falls in against them.
  • Keep plant and materials away from the edge.
  • Avoid underground services—use relevant service drawings, service locating devices and safe digging practices.
  • Provide ladder access to get in and out.
  • Make sure adjacent structures are not undermined by digging.
  • Check the excavation each day before work starts and after any event that may affect its stability, such as a fall of material or poor weather. Keep records so your workers can be sure it is safe to continue.
Keep Your Project on Solid Ground

Excavation projects require constant maintenance and risk management to stay on solid ground. Just one slip-up could cause the entire project to crumble.

Download our Daily Inspection Checklist for Trenches and Excavations to aid your construction sites safety.

If you wish to talk to an insurance advisor as to which steps to take next, call us on 0121 764 5500 or email info@adlerinsurance.co.uk to see how we can help protect your business.

Next Steps

Adler Insurance

Content creator for the Adler Insurance Group.