The paper presents the overall stability evaluation for a deep excavation in quick clay supported by flexible retaining structure (sheet pile wall) and ground improvement by lime-cement columns and vertical drains. The soil structure interaction analysis is performed using the finite element program Plaxis. The challenge of modelling the sloping layers with shear strength increasing linearly with depth is managed by using a special “vertical clusters” technique. Main conclusions from Plaxis analyses are as follows: Mohr-Coulomb model can be used to simulate pre-peak behavior of quick clay and the FE method can detect most critical failure mechanisms. The working sequences are monitored by lateral displacement (inclinometers), settlement and pore-water pressure measurements. Unfortunately, due to some site problems the quality of measurements is questionable. Despite some technical problems during the excavation work, the bottom of the excavation is now successfully closed by a concrete bottom slab and the structural work is in progress.