Prediction and performance of a ground freezing application to the rehabilitation works of an existing tunnel

The Cassia-Monte Mario railway tunnel, which runs through a hill in the northern part of Rome (Italy), has required invert demolition and reconstruction. The tunnel crosses heterogeneous sandy and silty soils below the water table. In order to prevent the ingress of water, the ground freezing technique was applied. The paper describes the design predictions based on simplified thermal analyses, laboratory tests and real-scale trial fields which were performed to integrate and validate the design predictions. Field tests were supported by automatic monitoring system implemented to measure the temperatures in the ground and deformation effects induced by freezing on the lining. The paper focuses on the role played by field tests which gave a decisive contribution to the correct and effective planning of the execution phase. This allowed to reach a better insight into the application of the ground freezing for underground works.