Risk management is of particular importance for the success of tunnelling and it is closely linked to the excavation method to be used and the work's specificities. The Conventional Excavation Method (CEM) and the Tunnel Boring Machine excavation method (TBM) have been competing for years, and the technical and scientific community has stated before that there are no studies analysing the differences between both methods with regard to health and safety levels. This means that there are no current studies on the importance of the “Health and Safety” criterion when selecting the excavation method. This Thesis intends to contribute to filling this gap.

In order to do so, the criterion “Health and Safety” has been analysed. On a first stage, the position of this criterion relative to the other criteria in the process of selecting the excavation method has been studied. On a second stage, the most typical accidents at work and occupational diseases in underground works (with both of the excavation methods) have been typified. On a third stage, risk and occupacional factors assessment, involving the identification, assessment and ranking of those, has been tackled. This way, a comparative assessment of risks and occupational factors has been carried out, comparing CEM and TBM. Three different scenarios were considered in order to fully understand the impact of the different variables. The first scenario analysed was the construction of a tunnel 3.5 km long, in a non-urban environment, and in a healthy rock mass without influence of water. Subsequently, constraints were introduced (such as heterogeneous rock mass, simultaneous works, use of explosives), which represent variables to the initial solution. In a third phase, the risk minimization measures were explored, with the goal of assessing their influence on the decrease of risks, for each excavation method.

In addition, a legislative proposal was prepared, to fill the legislative gap with respect to the subject under study.

The end result of the Thesis, therefore, is a full process to analyse the influence of the “Health and Safety” criterion in its several sides. It presents as an instrument that will allow all those involved to know the specificities of each method regarding this specific criterion.