Pre-grouting
Often pre-grouting is needed to reduce the inflow of water into the tunnel. The amount of water permitted into the tunnel is often based on environmental restrictions and sensitive areas above the tunnel.
Drill and Blast Technique
- The tunnel face is drilled (typically 100-200 holes) in a specific pattern using jumbo drilling rigs. The holes are normally 3-5 m long.
- Explosives are placed in the drilled holes and detonated to break the rock.
- After blasting, the muck (broken rock) is removed using loaders and haulage trucks.
Core elements include engineering geological mapping, controlled drill‑and‑blast excavation, pre‑grouting for water control (critical for subsea tunnels) and efficient mucking.
Jens Petter Henriksen
Prosjektdirektør Tunnel
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