Artificial ground freezing: Heat and mass transfer phenomena

The artificial ground freezing method is a waterproofing technique and/or temporary consolidation procedure used to realize the excavations of solid or fractured rock soils underground water in order to build tunnels, shafts and connecting galleries. The artificial freezing technique consists of circulating a coolant fluid with a lower temperature of the surrounding ground inside probes positioned along the perimeter of the gallery. In this way, the water contained in the soil pass from the liquid phase to the solid one by forming a block of frozen ground in surrounding area of the tubes. The authors have developed a 2Dnumerical model to analyze the heat and mass transfer phenomena in the ground, taking into account the water phase change process. The two-dimensional numerical model has been employed to analyse the phenomena occurring in three cross sections of the galleries. The aim of the work is to analyse the complex thermal phenomena occurring in the ground during the freezing stages and optimize the freezing process and optimize the various stages in the freezing activities and tunnel excavation.