Laboratory Testing and Numerical Modelling of the Dynamic Behaviour of Tagus River Sand

Abstract

In the framework of a third Tagus River crossing, through an immersed tunnel, advanced laboratory tests were performed on its highly liquefiable foundation sand, namely cyclic undrained torsional tests. The Manzari-Dafalias model, which allows simulating liquefaction on the Tagus River sand and is, therefore, central in the tunnel design, as well as the numerical work to calibrate the model and identify its most relevant parameters, are presented. Model parameters, their respective reference values and tests performed to determine directly most of the parameters, are introduced. A parameter sensitivity analysis, conducted through numerical simulation of triaxial monotonic drained tests and of cyclic undrained torsional tests, implemented both for the pre-liquefaction and liquefaction phases, is described. Finally, some parameters are determined by fitting the model to the laboratory results.