Collapse happens in seconds — how to make sure the ground can't bury anyone
An excavation can collapse in seconds, with no warning, burying or crushing anyone inside — so never assume the ground will stand unsupported. Prevent collapse by shoring, benching or battering to suit the soil and depth, keep people and spoil back from the edge, locate underground services before you dig, and inspect daily. Work where a person is in a space more than 1.5 m deep (and deeper than it is wide) is notifiable to WorkSafe.
Excavation failures are so dangerous because they happen fast — often with no warning — which leaves workers, and sometimes people nearby, almost no time to escape. The falling earth buries or crushes anyone in its path, causing death by suffocation or internal crush injuries.
The starting point for every excavation is simple: do not assume the ground will stand unsupported.
Choose your control to suit the soil type, the depth and the conditions, including weather:
| Control | What it means |
|---|---|
| Shoring | Supporting the sides with shoring or a trench shield so workers can enter safely. |
| Benching | Cutting the sides back into stepped levels to deal with loose soil. |
| Battering | Sloping the sides back to a safe angle so they will not collapse. |
No one enters an unsupported section of an excavation. Where shoring is used as the control, it must be designed by a suitably qualified professional engineer, made of sound and suitable material, and braced against displacement. Where shoring is impracticable, a registered engineer must certify that the precautions taken are adequate.
Some excavation is particularly hazardous work that must be notified to WorkSafe at least 24 hours before it starts, using the hazardous-work notification form. This includes any pit, shaft, trench or excavation where a person works in a space more than 1.5 metres deep and deeper than its horizontal width at the top, and any excavation where a face has a vertical height of more than 5 metres and an average slope steeper than 1 horizontal to 2 vertical.
Strike an underground service and you risk electrocution, explosion or flooding. Locate and mark services before you dig, dig away from them, and use safe digging practice such as hydro-excavation or potholing near known services. Run ground-breaking under a permit, and if an unidentified service is exposed, stop work and report it before going on.
Fence or barricade the excavation with barriers strong enough not to give way if someone leans or falls against them, and keep spoil, materials and plant at least 600 mm back from the edge. Provide safe access and egress. A fall into an excavation is working at height, so use edge protection. Dewater where flooding could occur, watch for exhaust gases, and treat a deep excavation as a possible confined space. A competent person must inspect the excavation before work each day and after any event — such as heavy rain — that could affect its stability.
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Collapse. An excavation can give way in seconds with no warning, burying or crushing anyone inside, so the ground must never be assumed to stand unsupported.
When a person works in a space more than 1.5 metres deep and deeper than its width at the top, or where a face is over 5 metres high with an average slope steeper than 1 horizontal to 2 vertical. Notify at least 24 hours before starting.
By shoring, benching or battering to suit the soil and depth. Shoring used as a control must be designed by a suitably qualified professional engineer, and no one enters an unsupported section.
Keep spoil, materials and plant at least 600 mm back from the edge, and use barriers strong enough not to give way if someone leans or falls against them.
Yes. Locate and mark services before digging, dig away from them, use safe digging practice such as hydro-excavation near known services, and stop and report if you expose an unidentified service.
