Abstract Risk management is of paramount importance for the success of tunneling works and it is linked to the main excavation methods used: the Conventional Excavation Method (CEM) and the Tunnel Boring Machine Method (TBM). Considering the importance of the “Safety and Health” criterion for the choice of the excavation method, the fact that this criterion is usually mostly focused on the structural component, and taking in account that there is no research showing the advantages of one of the methods over the other, this research intends to conduct a comparative risk analysis between both methods, taking into consideration the different constraints that might appear. In order for this comparison to hold true, a risk evaluation is presented, analysing 12 risks and 4 risk factors in 3 phases, so that the impact of the different variables can really be appraised. This research is made in a scenario of the construction of a 3.5 km-long tunnel in a non-urban area, with an unproblematic rock mass. The final result will be a detailed analysis of the influence of “Safety and Health” criteria, useful for both the technical and the scientific community, something that has never been done before.

Abstract Tunnelling has been used for several purposes for thousands of years. In the coming years the world's population will increase in the urban areas. So, the urban centres will have to adapt, in order to guarantee that their future population will have the necessary and sustainable growth. Due to the constraints for surface construction, also connected to environmental issues, this population growth will imply a greater use of the underground. With this optimal growth, the population of the cities will have better mobility, quality of life, and economic and social sustainability. In a first phase, this report will present a historic approach to tunnelling and its foreseeable future. Afterwards, we will present some considerations on the three factors which tunnelling impacts: mobility, quality of life and social sustainability. As a case study, we will analyse the 2nd phase of the construction of the Marão Tunnel (TDM) - the longest ever built in the Iberian Peninsula- and describe the options made regarding each of those factors. In this case study, the options implemented made it possible to successfully execute the works. For the industry, this work is important because it describes a successful management of the aspects under analysis.