Segmental Tunnel Lining Installation

Segmental linings are precast concrete or steel segments bolted together to form the permanent tunnel structure.
Segments are heavy — a single concrete segment typically weighs between 2 and 10 tonnes depending on tunnel diameter.
The segment erector on the TBM or a crane in the shaft lifts and positions each segment into the ring.
Finger and hand crushing injuries during segment handling and bolting are among the most common incidents.
Segments must be positioned in the correct orientation and sequence to achieve design tolerances.
Grout injection behind the completed ring fills the annular gap between the lining and the excavated ground.
Grouting under pressure requires controls to prevent blowout and uncontrolled grout release.
Segment storage in the shaft or at surface must prevent stacking collapse and ensure safe handling.
Bolt tightening must achieve specified torque values to ensure the ring performs structurally.
Gasket sealing between segments prevents groundwater ingress into the finished tunnel.

Crushing injuries	Segments weighing several tonnes create severe crushing and trapping hazards during lifting and positioning.
Structural performance	Incorrectly positioned or under-torqued segments compromise the tunnel lining integrity and groundwater seal.
Confined working	Installation takes place in the confined tunnel environment with restricted escape routes and limited space.

Do

Don't

Use the segment erector or crane to position all segments — never manual handling
Keep hands and fingers clear of segment joints during positioning and closure
Torque all segment bolts to the specified values and record the results
Install segments in the correct sequence and orientation as shown in the build drawing
Inspect gaskets on each segment for damage before installation into the ring
Follow the grout injection procedure including pressure limits and volume checks
Store segments safely in stacking frames that prevent toppling and allow safe handling
Brief the segment build crew on the ring sequence and specific hazards before each shift
Wear appropriate hand protection rated for the crushing risks during bolt-up
Report any damaged segments, cracked gaskets, or incorrect builds immediately

DON'T place hands between segments during erector positioning — use guide tools
DON'T install segments that are cracked, chipped, or have damaged gaskets
DON'T exceed grout injection pressure limits — blowout can cause serious injury
DON'T stack segments higher than the manufacturer's recommended limits on site
DON'T use undersized or incorrect bolts for segment connections
DON'T deviate from the designed ring build sequence without engineer approval
DON'T stand beneath a suspended segment during erector or crane operations
DON'T leave annular grouting incomplete — ungrouted sections weaken the tunnel
DON'T rush the build process — incorrect tolerances accumulate through the drive
DON'T ignore water ingress through gasket joints — report for investigation

See also: Tunnelling Safety Awareness | TBM (Tunnel Boring Machine) Safety

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