TUN/Specific/TBT-TUN-003

Microtunnelling Safety

Tunnelling & Shafts › Specific › Microtunnelling Safety

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Microtunnelling is a remotely controlled, guided pipe jacking method for installing small-diameter pipelines without open excavation.
The drive shaft is a deep excavation that functions as a confined space, requiring entry permits and atmospheric monitoring.
Jacking forces push pipes forward with extreme pressure through a thrust wall — the crush zone behind the jack is lethal.
The reception shaft receives the microtunnelling machine and must be prepared with the same confined space precautions.
Slurry systems circulate drilling fluid to remove spoil from the tunnel face, creating pressurised hose and pipeline hazards.
Ground settlement above the tunnel alignment must be monitored to detect movement affecting surface structures and services.
Laser guidance systems direct the machine — the beam must be managed to prevent eye injury to shaft workers.
The microtunnelling machine is remotely operated from the surface, but shaft work still requires workers in the confined space.
Noise from jacking operations and slurry pumps in the shaft requires hearing protection throughout the operation.
Spoil from the tunnelling process may contain contaminated material requiring COSHH assessment and special disposal.

Shaft as confined space	The drive and reception shafts are deep, enclosed spaces with atmospheric, drowning, and entrapment hazards requiring full permits.
Crushing force	Jacking rams exert massive force — anyone in the crush zone between the ram and pipe is killed instantly.
Ground settlement	Tunnelling disturbs the ground above — unmonitored settlement damages roads, buildings, and buried services on the surface.

Don't

Treat drive and reception shafts as confined spaces with full entry permits.
Monitor shaft atmosphere continuously for oxygen, methane, and toxic gases.
Maintain a strict exclusion zone behind the jacking ram during all pipe pushing.
Install ground settlement monitoring along the tunnel alignment before starting.
Manage the laser guidance beam to prevent eye exposure to workers in the shaft.
Inspect slurry system hoses, pipelines, and connections for leaks and pressure.
Wear hearing protection in the shaft during jacking and slurry pump operations.
Assess and dispose of contaminated spoil according to the COSHH assessment.
Maintain communication between the shaft, machine operator, and surface controller.
Brief the team daily on the tunnelling progress, hazards, and emergency procedures.

DON'T enter the shaft without a confined space permit and continuous gas monitoring.
DON'T position yourself behind the jacking ram during pipe pushing operations.
DON'T ignore settlement monitoring trigger levels — investigate exceedances immediately.
DON'T look directly into the laser guidance beam — it causes permanent eye damage.
DON'T use slurry equipment with damaged hoses or leaking pressurised connections.
DON'T work in the shaft without hearing protection during noisy jacking operations.
DON'T handle contaminated spoil without the PPE specified in the COSHH assessment.
DON'T allow communication breakdown between shaft workers and the surface controller.
DON'T skip daily briefings — microtunnelling hazards change with every metre of progress.
DON'T enter the reception shaft without the same confined space precautions as the drive.

See also: Tunnelling Safety Awareness | Pipe Jacking Safety

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