Tunnels (Historical Techniques)
Introduction
Some Roman tunnels have managed to reach us without many modifications until today, converted into true works of art and engineering, although they are much more discreet than bridges, their construction was much more complicated for the limited Roman technology.
They were built with a utility equal to the current one, since these galleries were excavated to allow the passage of a road through a mountain. We can distinguish at least three types of tunnel factory, in addition to semi-excavated passages, which can be found in several provinces of the ancient Roman Empire.
Technique
The Romans mastered the techniques of drilling and breaking rocks, usually putting them into practice in the excavation of mine galleries and aqueducts. At their disposal they had all the stonemasonry tools, such as maces, pickaxes, burins..., made of iron, whose shape was similar to that of current instruments.
In addition, they used the expansion-contraction game to break certain rocks, for which they heated them with live bonfires, to abruptly extinguish the fire with water and achieve the break. They also knew the properties of vinegar to weaken rocks, particularly limestone, for which they made grooves in the stone on which they poured the hot acetic acid and let it act, weakening the stone.
Works
Steps in gorges and gorges
The Roman road of the Great San Bernardo Pass has remains of the ancient Roman route, with side berms, bridges and tunnels.[1].
Passage excavated in the wall of the Danube gorge on the strategic route built by Trajan, specifically through a wooden platform, which partially protrudes over a cornice excavated in the stone of the gorge, raised somewhat above the average level of the river.
Tunnel excavated in the Apennine limestone with a length of 38 m on the Via Flaminia, between Rome and the Adriatic coast. Its profile is curved and was made under the empire of Vespasian.