ABSTRACT
ABSTRACT: The paper presents a very safe, cost-and time-effective tunnelling approach contrived and applied to the staged excavation of a tall and wide underground opening (cavern) within the Toledo Station, as part of the new Subway Line 1 in Naples. In this project the temporary support, usually provided by steel arches and shotcrete in aid to the frozen soil arch, was provided by the frozen soil arch alone by means of theArtificial Ground Freezing (AGF) technique until the completion of a first reinforced concrete liner following the excavation front (4 m behind), relying upon the high resistance of soil under freezing. In other words, the frozen soil arch acted both as structural and waterproofing element. With respect to traditional excavation technologies, the proposed solution proved to be very safe without penalizing time and economic aspects, plus allowing the thickness of the permanent support to be increased.
