Tunnels are special structures in the infrastructural road network. 'How can we guarantee that the structural safety of tunnels is sufficient and that the human safety is ensured?' This is a topic that continuously engages staff at TNO. It involves ongoing knowledge development and transfer.
What makes tunnels so different and thus special compared with other structures? As tunnels are underground, they are less accessible and more difficult to maintain than, say, a bridge. Furthermore, they are often a unique part of the road infrastructure. These days tunnels are designed to have a service life of 100 years. This involves all sorts of requirements with respect to the durability of the materials being used. In addition, a large part of the structure (the exterior) cannot be inspected, which gives rise to uncertainties. Owing to a lack of functional space, tunnels are often situated in urban areas that are densely populated. As a result, tunnels have a strong social impact. Just think of a disaster situation such as a fire or the explosion of hazardous materials in a tunnel. It is vital that the tunnel structure presents as low a risk as possible in a situation of this nature.
TNO is familiar with the standards and stays abreast of the continuously changing requirements imposed on tunnels. TNO's experts undertake various activities that contribute to the internal, external and structural safety of tunnels. To better quantify the life cycle of tunnels, they carry out product development and innovation related to structural systems. At their disposal they have a range of laboratories for testing specific situations and parts of tunnels. For examples of research related to the safety of tunnel structures, see under cases.