Underground urbanism - Historical and geographical overview

Underground urban planning is not conceived outside of "general" urban planning. Since its definition by Édouard Utudjian in the early 1930s, it has simply been a little-known part of urban planning. If, for the general public, urban planning has first and foremost an aesthetic dimension, conveying majesty and power, this dimension disappears as soon as the structures are invisible. But above all, urban planning is about satisfying major urban functions (access, mobility, hygiene, conviviality). Yesterday, security justified fortifications, watchtowers and guarded gates. Today, the city's primary mission is to satisfy the needs of its inhabitants, and only then those of visitors. There's no clear dividing line between architecture and urban planning; it's more a question of scale, from the building to the city, via the street, the block and the neighborhood.

More generally, the subsoil appears as the "hidden face" of the territory, a volume in truth. While most authors agree that the surface should be reserved for man, sustainable urban planning must make the most of the subsoil to create the best possible environment for man. By virtue of their position, the soil and subsoil provide the city with a natural infrastructure, gradually supplemented by built structures, roads and associated networks. But the subsoil can do so much more, hosting a significant proportion of urban functions and services. However, it is essential to plan the uses of underground space, as an integral part of the overall urban space, in space and time.

Following this historical and geographical panorama of underground projects, which are insufficiently known to engineers (and even less to elected representatives and civil society as a whole) because they are less visible than above-ground projects, or not visible at all, a second dossier is presented. will look at the conditions of practice, the why of using the subsoil: demand and supply, and the how: geological and legal constraints. The aim is to explain why the use of the subsoil can solve so many problems, and how it can be incorporated into urban planning practice. In addition, regional planning can also benefit from this dossier, as the "countryside" also has its own subsoil, with its traditional and future uses.

This dossier opens up a broader field for underground urban planning than has been the case up to now, a field that is mobilizing and will continue to mobilize more and more technical innovations, which in turn will expand the range of possible uses of the subsoil in the service of mankind.