Before the advent of tunnel boring machines, drilling and blasting was the only economical way of excavating long tunnels through hard rock, where digging is not possible. A tunnel boring machine that was used at Yucca Mountain. ... A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, Belgium A tunnel is an underground passage. ...

History

While drilling and blasting saw limited use in pre-industrial times using gun powder, it was not until more powerful (and safer) explosives, e. g. dynamite, and powered drills were developed, that its potential was fully realised. Wikipedia does not have an article with this exact name. ... This article is concerned solely with chemical explosives. ... Dynamite is an explosive based on the explosive potential of nitroglycerin using diatomaceous earth (Kieselguhr) as an absorbent. ... // Hand tools A bit and brace, a hand-powered drill. ...

Drilling and blasting was succesfully used to construct tunnels throughout the world, notably the St. Gotthard Tunnel, or the Jungfraubahn. The St. ... The Jungfraubahn (JB) is an 1000 millimetre gauge rack railway electrified at 3-phase 1,125 volts, which runs 9 kilometres from Kleine Scheidegg to the highest railway station in Europe at Jungfraujoch. ...

Procedure

As the name suggests, drilling and blasting works as follows:

A number of holes are drilled into the rock, which are then filled with explosive. Detonating the explosive will cause the rock to collapse and thus lengthen the tunnel.

Repeating these steps will eventually result in a tunnel.

The positions and depths of the holes (and the amount of explosive each hole recieves) are determined by a carefully constructed pattern, which, together with the correct timing of the individual explosions, will guarantee that the tunnel will have an approximately circular crosssection.