ABSTRACT
The construction of the new Porte Maillot station has been one of the most challenging phases of the EOLE project, the extension of the RER E (Regional Express Railway line) to the western part of Paris. This station is built in a highly complex urban environment, surrounded by numerous sensitive existing structures, particularly the Metro Line 1, which passes a few meters away from the new RER E alignment. During construction, a detailed monitoring system has been installed to track both ground and structure displacements (existing and new) to verify the consistency between measured displacements and those predicted based on design numerical models. Discrepancies in the displacements of the metro line during the initial construction phase have been highlighted, with higher settlement values during the installation of the diaphragm walls and lower heave values during the cut and cover excavation of the soil, which could lead to this structure exceeding the threshold values by the end of the station construction. To improve the prediction of the final deformations of the adjacent structures, a back analysis has been first performed to re-evaluate the geotechnical parameters of the soil, and the revised parameters used in a three-dimensional (3D) model developed in the FLAC3D numerical geotechnical software. The final settlements have been shown to meet the project requirements, and the model results have been confirmed by in-situ measurements after construction completion. In addition, the model has been also used to evaluate possible modifications of the final construction stages to define preventive measures, enabling the client, the French National Railways (SNCF), to make informed decisions.
