ABSTRACT
In the context of the design studies for the stations of the metro project of Line 16 of Grand Paris Express (GPE), the analysis highlighted the advantages of the asymmetrical bi-lobe geometry for two underground stations: Clichy-Montfermeil and Chelles.
The innovative and complex nature of these bi-lobed stations lies in the construction of an “underground” structure in the geotechnical context of the Paris region, defined by a high groundwater table as well as the earth pressure, and in the impossibility of maintaining a definitive full-height diaphragm at the junction of these lobes, which compromises the station’s functionality. Indeed, the props between the two lobes can be a solution if their positions did not affect the functional height under ceiling required.
Contrary to rectangular structures where, a 2D model can often be sufficient to study the structure’s behaviour, the study of bi-lobed stations requires a 3D finite element model of soil-structure in order to analyse the distribution of forces in all of the diaphragm walls.
The specific shape of these structures encourages the annular behaviour of the two lobes. However, their junction, commonly called “Y-Panel” due to its geometric appearance, is a specific area of diaphragm walls used to redistribute the orthoradial forces coming from these lobes, which requires a particular attention to design it, by considering the construction schedule. In order to answer the several questions about the dimensioning method of the “Y-panel”, this study will focus on one of two stations: Chelles.
