Calibration of the Creep-SCLAY1S Constitutive Model Parameters for Champlain Sea Clay in Quebec

ABSTRACT: The structured behaviour of Champlain Sea clay makes it extremely sensitive to strains that may destroy the bonds between soil particles. This soil behaviour can have significant effects on foundation design, but it cannot be easily captured using standard finite element models such as Mohr-Coulomb. The PLAXIS Creep-SClay1S constitutive model was developed to simulate the anisotropic, rate-dependent behaviour of soft structured soils including creep. This constitutive model is considered appropriate for the analysis of Champlain Sea clay due to its ability to simulate the bonding and destructuration process of natural clays. The Creep-SClay1S model was applied to predict settlement due to an embankment construction over Champlain Sea clay at a site in the region of Montérégie in Quebec. Design parameters required for the Creep-SClay1S models were calibrated against laboratory tests and field-testing measurements using the PLAXIS “Soil Test” module. The PLAXIS “Soil Test” module outputs (Deviator vs. Axial Strain, PWP vs. Axial Strain) were able to replicate the stress paths of CIUC triaxial tests with some reliability. The calibration showed that the depositional history of Champlain Sea Clay must be taken into consideration in the PLAXIS modeling. A summary of the calibrated input parameters for the Creep-SClay1S model is presented here. A comparison of settlement prediction using conventional settlement theory for embankment construction to settlement predicted using Mohr-Coulomb and the Creep-SClay1S model was undertaken. Results indicate that the settlement predicted by conventional settlement theory and Mohr-Coulomb may greatly underestimate the magnitude of settlement in Champlain Sea clays compared to the Creep-SClay1S model.