A simple hypoplastic model with loading surface accounting for viscous and fabric effects of clays

Abstract

This paper presents a simple hypoplastic model capturing mostly all salient features of clays: rate dependency, time dependency and inherent and induced anisotropy without being restricted to only viscoplastic clays. Therefore, due to the strain rate decomposition into three parts, nonviscous clays, that is, rate-independent clays, can also be simulated. The incorporation of a loading surface allows to capture the behaviour of normal and overconsolidated clays. The model requires eight material parameters, which are simple to calibrate from standard laboratory tests. In total, 77 simulations of five different clayey-like soils are compared with experimental data. The simulations contain one oedometer test with loading-unloading-reloading cycles, creep and relaxation stages, both undrained and drained triaxial tests in compression and extension, as well as eight incremental response envelopes capturing also the directional response of Beaucaire Marl clay. Some limitations of the model such as the description of temperature effects on the behaviour of clays are also pointed out. KEYWORDS clays, directional response of clays, fabric (inherent) anisotropy, overconsolidated clays, rate dependence, viscosity This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A high-cycle accumulation model for clay and its application to monopile foundations

“…For example, one could choose an elastoplastic model (e.g. Modified Cam Clay (MCC) model [11]), a hypoplastic model [46,74] or a barodesy model [50] for the simulation of a bearing capacity problem of a shallow foundation on clay. These models are only able to simulate monotonic loading for non-viscous clays, and as in detail discussed in [72], they would not capture the strain rate dependency typical for plastic clays (as is the case with soft marine clays).…”

Experience of determining the parameters of the elastoviscoplastic soil model

“…Merita Tafili and Theodoros Triantafyllidis proposed a simple hypoplastic clayey soil model that includes eight parameters that can be determined and to calibrated from standard laboratory tests [13].…”

Constitutive anamnesis model (CAM) for fine‐grained soils

“…Some authors 31,33,45,48,51 incorporate the relation $$M(\theta )=M_cg(\theta )$$ proposed first by Argyris et al 60 . In this regard, Figure 4 illustrates different approaches for the incorporation of the Lode angle dependency.…”

“…The critical state surface incorporated into the present model is defined through a general relation conform with other formulations, which are widely used in constitutive models 31,33,48,51 : $$\begin{equation} F_c{\left({\bm \sigma },\theta \right)}={\hat{{\bm \sigma }}^*:\hat{{\bm \sigma }}^*}-\dfrac{2}{3}M_{\bm \sigma }^2=0. \end{equation}$$The Lode angle dependency with respect to the stress state $$M_{\bm \sigma }=M(\varphi ,\theta _{\bm \sigma })$$ is established following Equations (9)–(11).…”