ABSTRACT
The twin-tube Caltanissetta tunnel (~4km), located on the SS 640 of Porto Empedocle, has been realized by the TBM “Barbara”, one of the largest and most powerful in Europe (diameter 15.08 m).
The paper will highlight how the whole implementation process of the work has been characterized by a continuous confrontation with safety issues in order to identify the optimal solutions. Before the excavation, the methodology of Technical Risk Analysis (TRA) was used to estimate the uncertainty of different solutions in terms of time and costs. During the excavation phase, following the occurrence of cracks on the prefabricated segments of the tunnel lining caused by the thrusts of the jacks for TBM advance, studies and analyses were carried out on the possible optimization of the construction methods. In addition, due to the complex geological, geotechnical and hydrogeological conditions of the area, a redistribution of the emergency exits has been necessary and compensated by the adoption of safety measures defined by the risk analysis of the tunnel, carried out according to the IRAM methodology.
