Espoonlahti metro station is part of the Helsinki-Espoo metroline extension to the west. The station was planned under the existing Lippulaiva shopping mall. Lippulaiva will be demolished, and a new shopping mall will be built on top of the Espoonlahti station. Two separate constructions sites on the same property (one above ground, one below) created challenges in excavation and construction. Detailed collaboration was required to complete both sites safely and without damaging the construction of the other site.

Rock mechanics design and simulations were performed to identify an excavation sequence that would be safe to complete, minimize delays in construction while also decreasing the risk of structural damage to concrete works etc. The rock mechanics interaction between the sites was simulated chronologically with the changing conditions due to proceeding excavations and varying surface foundation loads: first the metro station excavations below the existing shopping mall followed by the demolition of the existing shopping mall and excavation of the new mall simultaneously with the metro station, and finally the foundation loads of the new shopping mall after the metro station excavations were completed. Among other things, displacements, joint shear/opening and strain on the designed and existing reinforcement structures were monitored during the sequential simulations thereby identifying critical stages in excavation. Based on the simulation results, the excavation and reinforcement designs were adjusted accordingly. Simulation results also provided the reference values for on-site displacement and deformation measurements during the excavation.