A jumbo excavator is used during the construction of the City Panhandle tunnel under Stockholm to drill holes for explosives. As the name suggests, the drill-and-blast process works as follows: a number of holes are drilled into the rock, which are then filled with explosives.
The detonation of the explosives causes the rock to collapse.
The debris is removed, and the surface of the new tunnel is reinforced.
These steps are repeated until the required drilling is complete.
The locations and depths of the holes (and the amount of explosives each hole receives) are determined by a carefully designed pattern, which, along with the precise timing of each detonation, ensures that the tunnel has a nearly circular cross-section.
During operation, blasting mats may be used to contain the blast, suppress dust and noise, prevent rockfall, and sometimes to guide the explosion.