Modeling the viscoplastic behaviour of clays during consolidation: application to Berthierville clay in both laboratory and field conditions

To analyze the effects of strain rate and viscoplastic strain on consolidat ion of natural clay, this paper presents a nonlinear viscoplastic model in which viscoplastic behaviour is modeled by a unique effective stress (sigma (v)') - viscous strain (epsilon (v)) - viscous strain rate ((epsilon) over dot(v)) relationship. The proposed model can consider the effects of strai n rate and viscoplastic strain on consolidation, to take into account the d ifference in strain rate between laboratory and field conditions, and the c ombined processes of generation and dissipation of pore pressure during con solidation. This model can also predict the behaviour of clay during stepwi se loading, constant rate of strain, and relaxation of effective stress. Th e predicted values using numerical analysis are compared with measured valu es in laboratory tests and in situ, under an embankment built on soft clay at Berthierville, Quebec. It is possible to estimate the consolidation beha viour of natural clay with reasonable accuracy using the proposed nonlinear viscoplastic model.