The tunnelling industry has the means to make any "hole in the ground" almost to any size and shape that is requested. The main challenge is to integrate such solutions in the long-term development and urban planning. The underground solutions must be cost-effective to compete with surface alternatives and they must be safe and felt to be safe by the users. Only by ensuring that we are capable of providing safe underground structures will underground infrastructure be perceived to provide a sound internal environment. There is public confidence that the tunnelling industry is capable of producing tunnels and caverns to the satisfaction of the clients.
This paper discusses the challenges of designing and building large underground caverns needed for a further developing of the underground infrastructure. Underground caverns excavated into the rock mass require a strict control on a number of design parameters describing the rock mass quality and its ability to host large caverns. Many of these are typical rock mechanical parameters that are identified for any underground excavation. However, one particular rock mechanics parameters is of utmost importance when designing large underground caverns but to the surprise of the authors of this paper it is very often ignored and neglected by many, namely the in-situ stress conditions. This paper will particularly shed light the importance of including in-situ stress conditions in the design tasks. Therefore a particular focus of the article is directed to the understanding and utilizing of in-situ rock stresses to materialize such caverns. The paper will also present some examples to visualise the beauty of underground rock caverns and their use to serve the public and thus constituting a major asset to the society including the world largest man made rock caverns, the Gjøvik hall in Norway.