TUN/General/TBT-TUN-004

Shaft Sinking Safety

Tunnelling & Shafts › General › Shaft Sinking Safety

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Shaft sinking involves excavating vertical openings from surface to depth for tunnels or services.
Shafts can range from small access chambers to large structures over 20 metres deep.
The main hazards include collapse, falling objects, flooding, hazardous gases, and restricted access.
Ground conditions must be fully investigated before sinking begins to prevent fatal surprises.
Shafts become confined spaces once they exceed 1.5 metres deep and must be treated as such.
Support systems such as caissons, secant piles, or sheet piles prevent collapse during sinking.
The Confined Spaces Regulations 1997 and CDM 2015 both apply to shaft construction work.
Continuous gas monitoring is essential — methane, CO2, and H2S can accumulate at depth.
Safe access and egress must be maintained at all times via fixed ladders or personnel hoists.
All materials and equipment must be lowered by crane or winch — never thrown down a shaft.

Prevent fatalities	Shaft collapses, falls, and gas exposure have caused deaths in UK construction.
Confined space risk	Deep shafts create toxic or oxygen-depleted atmospheres that kill in minutes.
Legal compliance	Confined Spaces Regulations and CDM impose strict duties on planning and control.
Falling object danger	Objects dropped into open shafts are a constant hazard to workers below.

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See also: Tunnelling Safety Awareness | Confined Space Entry Procedures

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