Finite element prediction of long-term behaviour of a test embankment based on back-analysis of early stages

The paper presents the finite element modeling of a test embankment built at one of the construction sites of the 2016 Olympic Games in Rio de Janeiro, Brazil. The embankment was raised over 6 weeks to a height of 6.7 m, and was monitored during construction and in the following month. The experiment had to end after a month of measurements due to the need to develop the test area. Instrumentation consisted of electric piezometers, settlement plates and inclinometers. The subsoil featured a pack of sedimentary soils, including soft clays. Firstly, field and laboratory tests were evaluated for numerical modelling parameters, and a sensitivity study of the various parameters was carried out. Program PLAXIS was used with the most suitable soil models for the different soil layers. The time-dependent behaviour of the clayey layers followed Terzaghi’s consolidation theory for pore pressure dissipation coupled with a Buisman (1936)-type solution for viscous behaviour. The final analysis used parameters adjusted by back-analysis of measurements in the monitoring period (2.5 months) in a 3D model. This analysis was extended to 50 years, aiming to predict the long-term behaviour of the embankment. Results of the 50-year analysis indicated that after 20 years the excess pore pressures would have practically dissipated, but that the long-term settlement would be 2.5 times greater than that at the end of construction. Furthermore, the ground horizontal displacement would be about 4 times greater than that measured at the end of construction.