No abstract

An artificial ground freezing (AGF) technique in the horizontal direction has been employed in Naples (Italy), in order to ensure the stability and waterproofing of soil during the excavation of two tunnels in a real underground station. The artificial freezing technique consists of letting a coolant fluid, with a temperature lower than the surrounding ground, circulate inside probes positioned along the perimeter of the gallery. In this paper, the authors propose an efficient numerical model to analyze heat transfer during the whole excavation process for which this AGF technique was used. The model takes into account the water phase change process, and has been employed to analyze phenomena occurring in three cross sections of the galleries. The aim of the work is to analyze the thermal behavior of the ground during the freezing phases, to optimize the freezing process, and to evaluate the thickness of frozen wall obtained. The steps to realize the entire excavation of the tunnels, and the evolution of the frozen wall during the working phases, have been considered. In particular, the present model has allowed us to calculate the thickness of the frozen wall equal to 2.1 m after fourteen days of nitrogen feeding.

The multi-award-winning Toledo station on Metro line 1 in the Spanish quarter of Naples, Italy, has been described as one of the most impressive and beautiful in the world. Designed by architect Oscar Tusquets Blanca and completed in 2012, the station also uniquely serves as an underground museum, blending iconic architecture, contemporary artworks and 500-year-old archaeological remains. In the 5 years since its opening the station has won many awards and helped Naples win the 2019 World Tunnelling Congress. This paper first describes the excavation of the station’s unusually large platform access tunnel in unstable water-bearing soft rock and loose sand, which required a complex combination of cement–chemical grouting, ground freezing and extensive monitoring. It then explains how archaeology, architecture and art were successfully integrated into the resulting underground spaces.

No abstract

No abstract