Rock Mechanics Challenges in Underground Construction and Mining

The underground construction and mining industry are facing many geomechanics challenges. This keynote address presents an overview of some practical challenges, recent developments and some new technical opportunities. In mining, going deeper, increasing safety standards, and aiming for high productivity demands engineering to maximise value. In underground construction, geological complexities and mechanisation demand better integration of engineering to ensure ease of construction. Lack of engineering for constructability when tunnelling in weak or brittle rock at depth often leads to unnecessary delays and extra costs. Furthermore, brittle failing rock at depth poses unique problems as stress-driven failure processes often dominate the tunnel behaviour. Such failure processes can lead to shallow unravelling or to strainbursting modes of instability that cause difficult conditions for tunnel constructors. This paper summarises lessons learned during the construction of deep Alpine tunnels and highlights implications that are of practical importance with respect to constructability. Special attention is given to issues of rock behaviour identification and to the selection of appropriate rock properties for underground construction in brittle failing ground.