This study was performed due to the expansion of the facilities and services of Helsinki-Vantaa airport at Vantaa, Finland by Finavia. Part of the expansion included a new open pit parking facility, a new shaft and an underground connection to the airport rail terminal. In addition to the parking facility, new buildings were also constructed above the rail terminal. An unconditional requirement was set that at no time during the excavation work can the services of the airport or the rail line be disturbed.

Rock mechanics design and simulations were done in the design phase to estimate the rock mechanics interaction between the new excavations, existing structures and underground spaces. The impact of the building foundation loads was also studied. Together with displacements, joint shear/opening and strain on the designed and existing reinforcement structures were monitored during the sequential simulations thereby identifying critical excavation stages. Based on the simulation results, excavation and reinforcement designs were adjusted accordingly. Simulation results also provided the reference values for on-site displacement and deformation measurements during the excavation.