ABSTRACT
Due to the progressive degradation of the state of the tunnel, induced by several natural and anthropic factors, maintenance activities are of utmost importance to ensure good operational performances over time, increase the life of the structure and reduce risks. In this chapter, following a brief description of the main degradation phenomena, the inspections and monitoring activities required to keep under control the evolution of the state of the lining – and more in general that of all the materials involved – are illustrated. The main possible courses of action are then reported, distinguishing ordinary maintenance, that includes minor repairs and protective measures, and more costly and time-consuming extraordinary refurbishment works. Finally, specific emphasis is given to the design of refurbishment works.
