Tunnels and underground structures
- Project Owner: GRT Gaz
- Mission: Etudes d’exécution G3
- Cost of the mission: 34 k€ HT
- Mission date: 2014-2015
SUMMARY DESCRIPTION AND CHARACTERISTICS OF THE PROJECT
The study carried out by GEOS Ingénieurs Conseils relates to the laying of a Ø 1200 gas pipeline between the towns of Cuvilly and Betz in the Oise department. The pipeline crosses the SNCF tracks underground at five points in the municipalities of Rouvillers, Houdancourt, Rully and Ormoy-Villers.
The technique chosen for the five crossings is the use of a microtunnel over lengths of around 40 m and at depths of between 4 and 6 m.
MISSION
GEOS was commissioned to carry out partial geotechnical studies (G3 as defined in standard NF P 94-500 of November 2013) for five underground SNCF track crossings using a microtunnelling machine. These studies covered the following points in particular:
- Analysis and summary of available geotechnical data,
- Identification of geotechnical hazards and constraints for the project,
- Definition of the principles of the preparatory work to be carried out prior to sinking to ensure proper execution,
- Study of the influence of the excavation on the SNCF tracks: estimation of settlements using an analytical method and a finite element numerical method,
- Analysis of the construction conditions and design of the foundations for the sectioning stations,
- Calculation of the settlements induced by the lowering of the water table at the level of the SNCF tracks,
- Definition of excavation dewatering solutions to limit the impact on the tracks.
