A very large underground sports and events centre was excavated in Kuopio Finland. The multi-purpose centre provides a venue for events such as concerts, seminars, tournaments, major league and international matches. The centre was created by enlarging a small existing tunnel network. This required very detailed planning of the order of excavation and reinforcement to verify that the slowly emerging final shape of the caverns is sufficiently and continuously supported, the installed reinforcement is not unnecessarily loaded as the excavations proceed and temporary rock pillars are stable for work safety while easily removable. The simulations were performed in several stages and in tandem with rock engineering design before excavation. The designs were updated based on simulation findings to optimize excavation and reinforcement staging and to mitigate risks related to locally unstable rock mass volumes during excavations. After the excavations had begun the simulation was updated based on the surveyed geology and the results were compared to data of real rock mass displacements obtained from site monitoring points.

The simulation geometry included the existing tunnel network with accesses, new cavern volumes and new open pit excavations on top of the new cavern. The rock surface topography was interpreted from surveyed outcrops and percussion drillings. Rock quality and rock joint orientations and properties were interpreted from systematic geological surveys from the existing tunnels and core drillings through the volume of the new cavern. Intact rock properties were based on rock samples tested in the laboratory and the in-situ stress field on two stress measurements with a LVDT-cell. Rock reinforcement structures were based on the designs of the new caverns. The stability of the new caverns was simulated with building foundation loads on top of the cavern and to withstand a rapid large area pressure impact.

Numerical simulations were done with 3DEC to describe the behaviour of a blocky rock mass. Natural jointing of the rock mass was implemented with a DFN. The simulated excavations and installation of reinforcements were done sequentially following the true order of construction as closely as possible. Several aspects were monitored during the sequential simulations including but not limited to displacements, joint shear/dilation and strain of the designed and existing reinforcement structures, while critical stages of excavation were identified. The excavation and reinforcement designs were adjusted accordingly based on the simulation results. Simulation results also provided reference values for on-site displacement and deformation measurements during the excavations. A separate probabilistic study of potential key blocks and their required reinforcement was also performed.