The main objectives of developing soil models and numerical methods are to provide tools for predicting the field behaviour. This can only be justified against carefully selected case histories. This paper presents a study on porewater pressure and deformation responses in clays at the sites of two case projects, that is, an artificial Tarsiut Island on marine clay in the Beaufort Sea and Berthierville test embankment on soft ground in Quebec, all in Canada.
It has been reported that the excess porewater pressure in clay underneath Tarsiut caisson retained island increased for many months following completion of construction (with vertical load unchanged). Nobody has ever simulated successfully this phenomenon of excess porewater pressure increase under constant loading at the Tarsiut island site before. A newly developed three-dimensional (3-D) elastic viscoplastic (EVP) model (Yin and Graham 1999) is implemented in a finite element (FE) program to analyse the consolidation behaviour of the clays under Tarsiut island loading. The phenomenon of porewater pressure increase with time following the completion of the island construction has been successfully simulated. The mechanism of the porewater pressure increase due to creep is explained also in this paper. Finite element consolidation modelling of the soils underneath Berthierville test embankment is then carried out. It is found that the compression of the clay layer computed from the FE model is in good agreement with field measured values. Pore water pressures from the FE modelling are close to the measured values except for the value sat the initial loading stage.
The Tarsiut island was a man-built artificial island, located approximately 60 kilometres offshore with sea water depth approximately 21m. This artificial island consisted of four independent concrete box caissons set on an underwater sand berm.