Underground urbanism - Demands, offers, constraints and advantages

Many examples illustrate the ecological value of underground developments and their place in sustainable development.

All of them, from individual cellars to gas storage facilities, save surface space and energy. Building inside a large cavern saves on foundations, roofs and walls (as in the CNIT dome at La Défense). The traffic tunnel muffles vibrations, noise and odours. Under a crossroads, an underground passage saves time, fuel and pollution. In addition to energy, underground warehouses save on guarding, maintenance and insurance. More generally, greater use of underground space is essential today to combat urban sprawl and revitalize many city centers.

In a liberal economy, the law of supply and demand drives the market: the supply of underground space is hampered, firstly by its lack of visibility (except precisely when it comes to hiding and protecting), secondly by ignorance of both legal and technological possibilities, and thirdly by fear of unpleasant surprises in terms of costs and lead times. As a result, demand remains timid or even non-existent. To stimulate demand, we need to make our offer better known by highlighting its attractions.

The development of underground spaces is confronted with two types of constraints: the terrain and the social environment. On the one hand, "hard" sciences such as geology, hydrogeology and geotechnics, on which projects can be based, and on the other, human sciences, often referred to as "soft" sciences, including law. Without rapid changes in the law, which is always lagging behind economic and social developments, it will be difficult for the subsoil to play its part in making cities more sustainable.

Contrary to popular belief, the benefits of underground development include safety and economy. This dossier does not deal with design and execution, which are covered elsewhere.

readers may wish to refer to the previous dossier in the Éditions T.I. documentary database (cf. ) .