Studies on the environmental compatibility of conditioning agents for the reuse of the soil produced by the mechanized excavation of tunnels.

Mechanized tunnelling and excavated soil management are a combination that, in the last years, started to be considered an inseparable binomial: both in fact require extremely accurate planning, since there are many professional skills involved, there are risks must be foreseen for the workers involved and for the environment. and being particularly articulated the project approval and validation process. With particular reference to the excavated soil reuse, its design requires a deep understanding of the nature of the interaction phenomena between soil and chemicals commonly injected during excavation with TBM equipped with EPB technology. This interaction is responsible for both the variation of the physical and mechanical characteristics necessary to perform the excavation in a correct and safe way, as well as the environmental impact of the chemicals, the speed of their natural biodegradation and consequently the ways of re-using the same excavated soil allowed by current national regulations. Parallel to the site-specific experimental activities developed to support the Reuse Project for excavated soils and rocks, the development of an organic geotechnical, chemical and environmental study is particularly interesting. The general aim is the development of the scientific knowledge required to support Designers, Contractors, and Engineering Companies in a virtuous and efficient management of the excavated soils. In this article, after having briefly framed the problem from the regulatory point of view, are described the last guidelines on the methodology suggested to support of the planning of the reuse of soils and rocks. Finally, some results of a research activity carried out at the University of Rome Sapienza by GEEG Start-up in collaboration with Astaldi and an example of soil reuse in the Milan Metro M4 project are illustrated.