SPECIAL FOUNDATION SOLUTIONS FOR THE MAIN STAGE OF THE WORLD YOUTH DAY 2023, IN LISBON

This paper presents the foundation solutions adopted for the main stage of the World Youth Day 2023 in Lisbon. The stage was built above the old municipal solid waste landfill, sealed at the top by a HDPE geomembrane. This geomembrane restricted the use of deep foundation methods with impact on the urban solid waste landfill. The waste deposit rests over an alluvial layer, with weak geomechanical properties and variable thickness ranging about 12m at the main stage area. To mitigate differential settlements that could harm the structure behaviour during its set up and further utilization, a temporary preload landfill was built to anticipate settlements before the stage’s installation. During the preload phase, several monitoring campaigns were carried out with readings of topographic marks to calibrate the initial design assumptions. Based on the data obtained from the monitoring and on-site tests, the foundation solution for the stage was defined and designed. The foundation system for the main structure incorporates pre-cast hollow slabs, that can be reused after the event, and ductile iron driven micropiles. For the main stage cover, the foundations solution includes also ductile iron driven micropiles, reinforced with a central self-drilling bar, properly sealed into the Miocene layer at depth bigger than 30m, to accommodate tension loads.