The development of an underground station below the water table requires rigorous and careful planning. As such an in depth knowledge of the station construction designs and the related hydraulic behavior are required in order to design the most appropriated drainage system. Moreover, it is important to ensure the correct drainage of the excavation site to avoid liquefaction and to minimize water seepage. As an example of underground construction we consider the tunnel for the new line in the Barcelona metropolitan area (Línia 9) through the town of Prat de Llobregat in the Llobregat River’s delta, which is currently under development. Most of the tunnel sections are constructed with Tunnel Boring Machines (TBM) and the stations and the ventilation shafts are constructed using “Cut & Cover” technology between sheet pile walls. A typical station on the L9 line lies partially between the shallow and the main aquifer. Specifically, it is located in the middle layer which in made up of silts and clays. In order to design the most appropriated drainage system we present a methodology whereby we generalize the hydraulic problem. This method enables rapid and efficient estimation of fluxes as well as a general understanding of the problem in a simplified manner.

Peer Reviewed