Interpretation of an artificial ground freezing field trial at Fori Imperiali in Rome

This paper describes a field trial of artificial ground freezing (AGF) carried out in connection with the construction of Line C of Roma underground. AGF was one of the options considered for the temporary stabilisation of the ground during the excavation of Colosseo-Fori Imperiali Station. The field trial aimed at assessing the feasibility of AGF in the complex soil profile and groundwater regime of the subsoil of the historical centre of Roma by establishing the response of the subsoil to the imposed freezing loads, the ability to create a continuous frozen wall, and the associated coolant consumption. The extensive monitoring data were exploited to conduct a detailed analysis of the transient freezing process in the stratified subsoil and used to develop and validate a three-dimensional thermo-hydraulic numerical model. Special attention was given to defining and applying appropriate boundary conditions at the freezing pipes. The paper discusses the main factors affecting the time-dependent freezing process and explores the applicability of simplified two-dimensional models for the Fori Imperiali AGF field trial.