The most legendary French bridges: Le Pont Du Gard
This may seem surprising when one looks at the constructions that are emerging in the four corners of the world today. But thanks to its surprising achievements that defy time, France still stands as a key nation in terms of civil engineering!
We will share with you anecdotes and technical details about three of the greatest bridges that have marked the history of civil engineering in France and around the world!
Our first file will focus on the Pont du Gard, one of the most visited civil engineering structures in the world!
Back on the history of the Roman aqueduct
Even today, the Pont du Gard, located in the beautiful region of Occitania, is the source of many superstitions and legends. Many people ask themselves “How did the book survive the time while keeping the majority of its structure intact? “Or” How, with the means of handling of the time was it possible to beat the height records for the construction of an aqueduct? ”
The history of the oldest surviving French art work begins in the 1st century AD At this time, the entire region of southern France is conquered by the Romans and the city of Nîmes can no longer meet the needs of its inhabitants. water of its population.
Indeed, the fountain of Nemausus located at the foot of Mount Cavalier is not enough to supply water to the inhabitants but also the baths of the city.
To remedy this problem, Roman engineers seek various solutions to bring water from another source to the city. They decided to build an aqueduct connecting the source of Uzès to the city of Nîmes.
A real technical feat because you have to circulate water over fifty kilometers and with an extremely low altitude (about 25cm per km).
For this giant project, engineers must also take into account the significant obstacles that the roach valley, the surrounding forests and the inevitable realization of several tunnels.
The aqueduct fulfills its function until the fifth century. It was then converted into a toll in the Middle Ages and finally a road bridge between the eighteenth and twentieth century.
It was not until the early 2000s that this great site in France was preserved in view of its rich history. It has since been reserved for tourist purposes and can only be visited walking.
The Pont du Gard in a few figures
49m: it’s the height of the bridge, a record for the Roman era!
275m: it is the length of the work located between 2 mountains, above the Gardon.
3: the number of different levels in the aqueduct. It is actually a superposition of 3 bridges to reach the necessary height.
64: the total number of stone arches built for the Pont du Gard.
21,000 m3 of limestone was extracted from the quarries.
50,000 tons estimated for this work made of stones.
15: number of years needed for the construction of the aqueduct between Uzès and Nîmes. The Pont du Gard shipyard is estimated at around 5 years.
450: years of use of the aqueduct before being abandoned.
1898: it is only that year that the aqueduct receives the name of Pont du Gard.
December 6, 1985: date the stone work is listed as a UNESCO World Heritage Site.
1.5 million visitors roam the central path of Pont du Gard each year.
The secrets of the construction of this two-thousand-year-old stone bridge
To begin the construction of this Roman monument, it was first necessary to find the stones, the main component of the structure. Luckily, the builders had a stone quarry with quality rocks within 600 m of the construction site. It was then sufficient to transport the stones through the river before cutting them to the proper dimensions.
The assembly of the bridge over roach gorges was done dry, that is to say without the use of mortar between the stones to weld the elements together. The assembly process consisted in polishing the stone with abrasive red sand and then stacking them thoroughly.
During construction, builders always began with the largest arches and used the heaviest stones to form the base of the piers. Then, a wooden formwork, also called a jig, was positioned to assemble the stones constituting the arch.
When we go to the site now, we realize that the stones constituting the arches were numbered. A specific location was assigned to each of them according to their shape so that the entire structure holds in place by simple compression effect.
In the case of the aqueduct, a structure used to carry water through canals and channels, it was located on the 3rd floor of the Pont du Gard. Each of its piers had been coated with tile concrete (hydraulic concrete) to minimize leakage and loss of water.
However, 2000 years after the laying of the first stone, the structure seems to show some signs of weakness. We note in fact that the Pont du Gard is no longer rectilinear but begins to curve. So how will the vestiges of this Gallo-Roman bridge, an extraordinary heritage of the Nîmes region, be preserved, and how will today’s civil engineers intervene to preserve the formidable Pont du Gard?
The Matière® company is mainly specialized in concrete works and in the manufacture of large metal bridges for more than 25 years. Works of art represent the major part of its activity. In 2004, the Cantal company even developed a concept of prefabricated modular bridges that can be installed in record times, the Unibridge® bridges.
Matière® could therefore contribute its know-how to help preserve this exceptional heritage.