Flexible response to difficult ground and controlled tunnelling technology

Tunnel construction is a complex interaction between structural design concepts and flexible response to ground reactions in advanced tunnelling technology. The concept of structural design for tunnels is of increasing importance in advanced tunnel construction technology. There are different approaches in design modeling taking into account cross section geometry and overburden. The size of tunnels represents one essential input among others. In order to view into reproducable conditions, this paper deals with two specific examples of transportation tunnels being located in Europe and South America. However, they could be located anywhere else, Such tunnels can be situated in shallow, shallow deep and deep conditions of overburden. Shallow tunnels (Example 1) require the ability to take a greater number of different loading conditions, using stiff and rigid lining concepts. Deep tunnels (Example 2) do relate to loading conditions on the lining showing extended deformation behaviour. Deep tunnels have an essential need for implementation of flexible responses due to observations. At both of the two examples there happened to be failures respectively collapses of the tunnel lining and the surrounding ground. This offered the chance to study the failure mechanisms and to learn for the future. There were no fatalities involved in both cases. Shallow deep tunnels show benefits in the design both from the shallow tunneling and the deep tunneling philosophy. They are designed to use as a minimum requirement standard support measures. Depending on the ground they need to be supplemented by additional support measures as envisaged in the design under the requirements of standard safety needs during all constructions stages.