ABSTRACT
Several chemical products are necessary during the mechanized tunnelling with TBM-EPB, mainly for three applications: soil conditioning (important for a fast and safe advance of the EPB), backfill grouting of the annular space that is created between the segmental concrete lining and the surrounding soil or rock mass, and tail brushes sealing (to avoid the ingress of material such as water, foam, soil, etc. into the TBM working area).Each one of these chemical products inevitably brings a certain degree of environmental impact, for example against the underground water or the excavated muck which needs to be disposed in a final destination. MAPEI have been working with its R&D laboratories to develop new products and new technologies that are able to reduce this impact, which can be measured in terms of lower eco-toxicity against terrestrial and watery organisms, quicker biodegradability, and lower emission of CO2 equivalent gases, which are responsible of the global warming (Carbon Footprint). Several examples will be described where technological and environmental innovations in soil conditioning, backfill grout and tail brushes sealing have allowed a more “environmentally friendly” excavation with EPB machines, without impacting the typical technical performances in any way.
