8This paper focuses on constitutive and numerical modeling of strain-rate dependency in natural clays 9 while also accounting for anisotropy and destructuration. For this purpose the SANICLAY model that 10 accounts for the fabric anisotropy with the additional destructuration feature that accounts for sensitivity 11 of natural clays, is considered as the reference model. An associated flow rule is adopted for simplicity. 12The model formulation is refined to also account for the important feature of strain-rate dependency using 13 the Perzyna's overstress theory. The model is then implicitly integrated in finite element program 14 PLAXIS. Performance of the developed and implemented model is explored by comparing the simulation 15 results of several element tests and a boundary value problem to the available experimental data. The 16 element tests include the constant strain-rate under one-dimensional and triaxial conditions on different 17 clays. The boundary value problem includes a test embankment, namely embankment D constructed at 18 Saint Alban, Quebec. For comparison, the test embankment is also analysed using the Modified Cam-19 Clay (MCC) model, the SANICLAY model, and the viscoplastic model but without destructuration. 20 Results demonstrate the success of the developed and implemented viscoplastic SANICLAY in 21 reproducing the strain-rate dependent behavior of natural soft soils. 22 (M. Taiebat), elisapoletti@civil.uminho.pt (E. Poletti).
17]). Time-dependency is usually related to the soil viscosity that could lead to particular effects such as 52 creep, stress relaxation, and strain-rate dependency of response. Time-dependency of soil response can be 53 observed experimentally by means of creep tests, stress relaxation tests, or constant rate of strain (CRS) 54 tests [18]. Rate-sensitivity is a particular aspect of time effect that has been investigated extensively; it 55 3 influences both strength and stiffness of soils. Various studies using CRS tests have shown how faster 56 strain rates for a certain strain level lead to higher effective stresses; also, the general observation, 57 particularly in soft soils, is that higher undrained strengths can be achieved by increasing the loading rate 58 (e.g., [16][17][19][20]). The reported observations from laboratory studies all imply that consideration of soil 59 viscosity effects could be key for correct prediction of long term deformations in field conditions; although, 60 neglecting soil viscosity seemingly provide sufficiently correct predictions in short-term [21]. Landslides or 61 long-term deformations of tunnels and embankments on soft soils are examples of common practical 62 problems where a sustainable remediation and/or design solution can only be achieved if time-dependent 63 behavior of soil is taken into consideration. 64 In order to account for the time-dependency of soft clays' behavior, various frameworks can be found 65 in the literature. Among a number of popular frameworks such as the isotache theory of Šuklje [22] or the 66 non-sta...