Back to Archaeology and the city of today - Choose and protect
After assessment in concert with the technical studies branches, that is, after several exploratory excavations have been carried out to define the nature of the remains, how deep they are buried, their thickness and the nature of the ground that bears them :
  • Either it appears that the remains are well enough buried to let construction go ahead as planned;
  • Or, special foundations can be put in place to ensure the preservation of the remains beneath the new buildings.
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Special foundations
If it turns out that specific foundations only preserve part of the remains, a preventative archaeological excavation is carried out to protect the information destined to disappear. Several foundation building techniques can be used on the same project according to the nature of the remains to be protected: their depth, the weight and design of the new buildings, their environment. Thus today, there are five special types of foundations supporting the Musée archéologique de Saint-Romain-en-Gal. During the past fifteen years numerous public and private buildings have been built on special foundations in the Vienne urban area. Click to enlarge 
Management of the Vienne urban area’s archaeological heritage
Two techniques are currently being used :
  • One is "ribbed, reinforced frames, on restored and compacted soil". This technique completely preserves the remains, if there is enough space between the top of the remains and the base of the foundations. In some cases, the finished floor may be raised in comparison with the surrounding ground.
  • The other is "steel-reinforced piles driven in and connected by horizontal beams or longitudinal girders". This technique is only acceptable if the intervals between the piles (most often between 9 and 11 m.) are wide, for the entire thickness of the remains they are driven through is completely destroyed. If the intervals are too narrow they will prevent any future archaeological analysis of the remains, if they were to be excavated during the demolition of the building. Nevertheless, the pile driving technique sometimes has to be used, for example, to avoid any differential subsidence when there are adjoining ancient buildings. Generally the piles are sunk blind : the width of the intervals between them allows for a very low destruction rate.
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