Designing a pre-load embankment for the construction of a stage over a sanitary landfill founded in soft soils

Abstract

For World Youth Day event in 2023 (JMJ), the organizing committee selected an area in Parque das Nações that met the imposed requirements, notably in terms of area (for 1 million spectators) and proximity to the Lisbon center. This area, on the other hand, has the distinction of being a sanitary landfill, which was sealed in 1997 as part of the EXPO98 interventions, and which previously, in 1995, experienced a large-scale landslide in the direction of the river, with a front of 300 m of extension, enveloping the foundation up to significant depths. The fundamental cause of the landslide, according to studies undertaken at the time, was the low undrained strength of the foundation's soft soils that were still in the subconsolidation phase, particularly at the deepest levels. Considering this scenario, LNEC performed limit equilibrium stability analyses as well as three-dimensional stress and strain finite-element analyses to estimate the magnitude and evolution of the settlements of the JMJ stage to be built in the southern area. The analyses carried out, the results of which are presented in the article, revealed the need of a pre-load embankment and were used to define criteria for the constructive phasing of the work, which was inherently dynamic and based on the outcomes of the monitoring system installed on site. Finally, values obtained from the monitoring system installed during the construction phase are compared to the values estimated during the design phase.