Excavation phases

Excavation of a tunnel

The same work phases are repeated in a certain order when a tunnel is excavated. The duration of a work cycle described below depends on the type of bedrock, and it can last from about six hours to a couple of days.


First, the bedrock is prepared for drilling by grouting.


Drilling and charging

Next, a drilling jumbo drills enough holes in the bedrock with varying lengths. The length of a so-called break is 0.5–6 metres.


Blasting and ventilation

Small amounts of explosive material placed inside the holes are blasted in a carefully planned order. The duration of the blasts is 6–20 seconds depending on the number of holes blasted at a time. The tunnel is ventilated after the blasts.


Loading and transport

Loose excavated rock is transported from the tunnel.



A special vehicle removes any loose rocks from the walls so that the tunnel can be accessed again safely to perform pre-grouting for the next drilling.