Constitutive modelling of unsaturated soils

Laloui, Lyesse; Geiser, F.; Vulliet, L.

doi:10.3166/rfgc.5.797-807

Cited by 5 publications

(4 citation statements)

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“…The constitutive variables are linked. Continuity of constitutive variables and behaviour is not assured at the saturated/unsaturated transition.The hydraulic component of the model is independent of the mechanical component; specific effects of degree of saturation are not included.The increase of strength with suction is a result of the constitutive variable definition.Strength and elastic behaviour can be unified with an adequate selection of the FCVKohgo et al (1993);Modaressi & Abou-Bekr (1994);Pakzad (1995);Modaressi et al (1996);Geiser et al (2000);Loret & Khalili (2000;Laloui et al (2001);Sun et al (2003);Russell & Khalili (2006);Masin & Khalili (2008) III (ó t ) ij À p g ä ij þ ì 1 (s,Jommi & di Prisco (1994);Bolzon et al (1996);Jommi (2000);Wheeler et al (2003);Gallipoli et al (2003);Sheng et al (2004);Tamagnini (2004);Laloui & Nuth (2005); Pereira et al(2005);Oka et al (2006);Santagiuliana & Schrefler (2006);Sun et al (2007aSun et al ( , 2007b;Kohler & Hofstetter (2008);Buscarnera & Nova (2009)…”

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confidence: 99%

Soil–environment interactions in geotechnical engineering

Gens¹

2010

Géotechnique

393

198

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The range of problems that geotechnical engineers must face is increasing in complexity and scope. Often, complexity arises from the interaction between the soil and the environment – the topic of this lecture. To deal with this type of problem, the classical soil mechanics formulation is progressively generalised in order to incorporate the effects of new phenomena and new variables on soil behaviour. Recent advances in unsaturated soil mechanics are presented first: it is shown that they provide a consistent framework for understanding the engineering behaviour of unsaturated soils, and the effects of suction and moisture changes. Building on those developments, soil behaviour is further explored by considering thermal effects for two opposite cases: high temperatures, associated with the problem of storage and disposal of high-level radioactive waste; and low temperatures in problems of freezing ground. Finally, the lecture examines some issues related to chemical effects on soils and rocks, focusing in part on the subject of tunnelling in sulphate-bearing rocks. In each case new environmental variables are identified, enhanced theoretical formulations are established, and new or extended constitutive laws are presented. Particular emphasis is placed on mechanical constitutive equations, as they are especially important in geotechnical engineering. The lecture includes summary accounts of a number of case histories that illustrate the relevance and implications of the developments described for geotechnical engineering practice.

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confidence: 99%

Soil–environment interactions in geotechnical engineering

Gens¹

2010

Géotechnique

393

198

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“…For the description of granular materials, several elastoplasticity models have been established that account for kinematic or isotropic hardening properties, such as the models developed by Vermeer (1978), de Boer (1988, Kim and Lade (1988), Lade and Kim (1988), Ehlers (1991Ehlers ( , 1995, and Ehlers and Müllerschön (2000). Furthermore, taking into account the special properties of partially saturated soil, Alonso et al (1990), Bolzon et al (1996), and Laloui and Nuth (2005) postulated that the yield surface within the elastoplastic theory is a function of the stress state as well as the pore-water saturation. We proceeded from the single-surface yield criterion proposed by Ehlers (1991Ehlers ( , 1995, which is downward compatible to other plasticity models, such as the well-known model of Drucker and Prager (1952) or the von Mises (1928) yield conditions.…”

Section: Computati On Of Slope Movements Initi Ated By Rain-induced Smentioning

confidence: 99%

Computation of Slope Movements Initiated by Rain–Induced Shear Bands in Small–Scale Tests and In Situ

Ehlers

Avci

Markert

2011

Vadose Zone Journal

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Computational investigations of the complex flow and deformation processes of natural slopes within a continuum‐mechanical approach become more and more important due to an increasing number of slope movements and slope failure situations caused by heavy rainfall events. Numerical simulations of hillslopes can support the detection of various coupled failure mechanisms by simply changing the initial and boundary conditions of the considered initial‐boundary‐value problem. This procedure can contribute to a deeper and better understanding of various complex slope failure processes. In this study, the slope system, generally understood as an unsaturated soil, was considered as a triphasic material consisting of a soil skeleton, such as sand, a pore liquid, such as water, and a pore gas, such as air. The model was embedded in the well‐founded theory of porous media, while numerical solutions were realized by use of the finite‐element solver PANDAS. Proceeding from cohesionless sand as the basic soil under study, the material parameters governing the soil behavior were taken from triaxial experiments on dry sand specimens performed under homogeneous loading conditions, whereas the parameters governing the hydraulic behavior were determined by experiments on saturated soil specimens under nondeforming conditions. Furthermore, numerical investigations of slope failure scenarios under different loading conditions were compared with each other to find out how the pore water influences the failure behavior. The computations reveal a strong coupling between the soil deformation and the hydraulic behavior during failure processes. Finally, the flow and deformation behavior of the natural Heumoes slope in Ebnit situated near Dornbirn in the eastern part of the Voralberg Alps (Austria) was studied qualitatively. Unfortunately, this slope is still in motion.

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“…The most commonly used combinations are (i) net stress σ net = σ − u 1 1 and suction u a − u w , (ii) an effective stress σ′ and suction u a − u w , while exceptionally the couple (iii) ‘saturated effective stress’ σ − u w 1 and suction u a − u w was proposed by Laloui et al . 6.…”

Section: Introductionmentioning

confidence: 99%

An unsaturated soil model with minimal number of parameters based on bounding surface plasticity

Morvan

Wong

Branque

2009

Num Anal Meth Geomechanics

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SUMMARYThis paper presents a constitutive model for unsaturated soils with only 13 parameters. Its development is based on the concept of bounding surface plasticity under a critical state framework. The definition of effective stress via an equivalent pore pressure and the introduction of suction effects into a general plastic hardening mechanism are inspired from the work of Pereira et al. (Ph.D. Thesis, 2005) and that of a few others. Despite the minimal number of parameters, this model can simulate correctly complex volumetric behaviour and post-peak softening, as well as a few other classic typical behaviours of unsaturated soils. The model is validated using experimental data both on saturated and unsaturated soils. Its efficiency has been highlighted by comparing its outputs with those from the Barcelona Basic Model and from another advanced model CJS-NS. The numerical studies revealed the necessity of additional experimental data for a more complete validation of the model and its future improvement.

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Constitutive modelling of unsaturated soils

Cited by 5 publications

References 0 publications

Soil–environment interactions in geotechnical engineering

Soil–environment interactions in geotechnical engineering

Computation of Slope Movements Initiated by Rain–Induced Shear Bands in Small–Scale Tests and In Situ

An unsaturated soil model with minimal number of parameters based on bounding surface plasticity

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