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  • Setec-Terrasol

    Extension 11 – Adaptation of the Mairie des Lilas Station

    Paris, France

Project Summary

Project
As part of a 6-kilometer extension along line 11 of the Paris metro, two new access points are being added at the existing Mairie des Lilas Station. The EUR 15 million project involves designing and constructing shafts and tunnels to intersect with existing infrastructure. Setec-Terrasol was retained to design the two access points to be constructed while the metro line and station remain open. To optimize project management, minimize risks, and accommodate the complex soil structure and challenging geometry, Setec needed to adopt a 3D numerical modeling approach.


Solution
Setec used PLAXIS to create two 3D geotechnical models, one for each access point. Using Bentley’s geotechnical engineering application, the team accurately modeled the new works and real geometry of existing underground structures. The software’s robust modeling and analysis features enabled Setec to use the models to simulate the soil behavior and project phasing, including installation of temporary supports, to ensure all work could be completed while the metro and station remained operational.


Outcome
Using PLAXIS, Setec generated two complex models to define displacement thresholds and justify feasibility of the project. PLAXIS helped the team quickly and precisely identify the structures expected to undergo faster settlement, when compared to using 2D calculations. The application improved the project’s reliability and security while reducing costs. Construction work on the principal access is underway. Based on the accurate geotechnical analysis model created with PLAXIS, on-site works show low impact on existing underground infrastructure and low building settlement, as predicted.


Software
PLAXIS facilitated accurate simulation of different soil layers and their behavior, enabling Setec to provide a reliable estimate of the impact and phasing of the construction works. The automated mesh and robust calculation features of the software optimized modeling of the complex 3D geometry and accelerated analysis to complete the feasibility study within the limited timeframe. Using the 3D geotechnical models provided access to results that not only are more correct, but also are more comprehensive compared to 2D methodologies, contributing to the overall success of the project.

Project Playbook: PLAXIS
Outcome/Facts
  • Setec used PLAXIS to establish 3D geotechnical models of two new access points at the existing Mairie des Lilas Station along the line 11 extension of the Paris metro.
  • Using Bentley’s geotechnical engineering application to model the complex 3D geometry and study the soil complexities optimized integration of the new and existing infrastructure.
  • The comprehensive modeling and analysis features facilitated accurate simulation of work phases, justifying temporary support and displacement prediction while reducing project costs.
Quote:

  • “The 3D approach [using PLAXIS] made it possible to take into account the obvious three-dimensionality of the problem and to more correctly simulate the phasing of the work and the soil/structure interactions between the different structures.”

    JP Janin Technical Engineer Setec-Terrasol