ABSTRACT
Within transportation infrastructures, stations general layout and depth are influenced by the tunnel alignment and functional requirements. In dense urban area, site conditions can also strongly constrain the location and dimensions of the worksite and thus the structures. In this context, respecting the deformation thresholds of vulnerable neighbouring structures becomes a significant challenge.
The degree of complexity increments when the structure to design is located in a complex geomorphological area which requires specific geotechnical considerations, such as uneven ground load behind the retaining walls, pushing clay and altered parameters.
This paper presents the design issues of a station characterized by a four-lobe shape which ensures significant circular stiffness of the retaining structure, while providing enough functional space. Yet, lateral caverns have been added at platform level to increase the passenger area.
Given the geological conditions, the vulnerable surroundings, the station complex geometry, along with the considerable depth of the structure (>50m), several advanced 3D numerical simulations have been performed to accurately assess the deformations due to excavations.
Modeling the initial stress state of the ground should be based on a comprehensive understanding of surrounding structures and their history of reinforcement. This is the starting point for the staged calculations to study this critical point of the project: respecting the damage thresholds of adjacent very vulnerable railway tunnel. This challenge was addressed by conducting a sensitivity study using a simplified model. This facilitated the testing of solutions capable of effectively reducing deformations beneath this structure, including retaining walls geometry, construction sequence, discussion on ground behaviour model, soil treatment, and more.
The results of the various numerical analysis comparing different technical configurations led to find a robust design solution that respects all structural/functional requirements as well as the surrounding constraints.
