ABSTRACT
Artificial ground freezing (AGF) in a horizontal direction has been employed in Naples (Italy) to ensure stability and waterproofing of the soil during excavation of tunnels connecting two lines of the Naples metro system. The artificial freezing technique consists in circulating a coolant fluid, with a temperature lower than that of the surrounding ground, inside probes positioned along the perimeter of the gallery. The water contained in the saturated soil solidifies and forms a block of frozen ground in the area surrounding the probes. To analyze the heat and mass transfer phenomena in the ground the authors have developed a 2D numerical model. This model taking into account the water phase change process and has been employed to analyse the phenomena occurring in five cross sections of the galleries. The aim of the work is to analyse the thermal phenomena occurring in the ground during the freezing stages and optimize the freezing process. In order to do that, the authors have taken into account the phases to realize the entire excavation of the two tunnels and the evolution of frozen wall during the working phases.
