Hydro-mechanical modelling of landslides with a material instability criterion

Lignon, Sylvain; Laouafa, Farid; Prunier, Florent; Khoa, Huynh Dat Vu; Darve, Félix

doi:10.1680/geot.7.00121

Cited by 52 publications

(38 citation statements)

References 27 publications

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“…Laouafa and Darve ([23,40]) presented similar results by modeling heuristic slopes. More recently, Lignon et al [41] used this criterion to model of real landslides by taking into account unsaturated soil. In these finite element analyses, the second-order work is computed at each integration point.…”

Section: Physical Interpretation Of the Previous Resultsmentioning

confidence: 99%

Bifurcation modeling in geomaterials: From the second‐order work criterion to spectral analyses

Prunier

Laouafa

Lignon

et al. 2008

Num Anal Meth Geomechanics

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SUMMARYThe present paper investigates bifurcation analysis based on the second-order work criterion, in the framework of rate-independent constitutive models and rate-independent boundary-value problems. The approach applies mainly to nonassociated materials such as soils, rocks, and concretes. The bifurcation analysis usually performed at the material point level is extended to quasi-static boundary-value problems, by considering the stiffness matrix arising from finite element discretization. Lyapunov's definition of stability (Annales de la faculté des sciences de Toulouse 1907; 9:203-274), as well as definitions of bifurcation criteria (Rice's localization criterion (Theoretical and Applied Mechanics. Fourteenth IUTAM Congress, Amsterdam, 1976; 207-220) and the plasticity limit criterion are revived in order to clarify the application field of the second-order work criterion and to contrast these criteria. The first part of this paper analyses the second-order work criterion at the material point level. The bifurcation domain is presented in the 3D stress space as well as 3D cones of unstable loading directions for an incrementally nonlinear constitutive model. The relevance of this criterion, when the nonlinear constitutive model is expressed in the classical form (d = Mdε) or in the dual form (dε = N d ), is discussed. In the second part, the analysis is extended to the boundary-value problems in quasi-static conditions. Nonlinear finite element computations are performed and the global tangent stiffness matrix is analyzed. For several examples, the eigenvector associated with the first vanishing eigenvalue of the symmetrical part of the stiffness matrix gives an accurate estimation of the failure mode in the homogeneous and nonhomogeneous boundary-value problem.

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Section: Physical Interpretation Of the Previous Resultsmentioning

confidence: 99%

Bifurcation modeling in geomaterials: From the second‐order work criterion to spectral analyses

Prunier

Laouafa

Lignon

et al. 2008

Num Anal Meth Geomechanics

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“…This criterion has been applied recently to the Petacciato and Trevoux landslides by Lignon et al (2009). The authors concluded that the second-order work criterion enables successful prediction of the primary unstable zones on these slopes that may result from a long rainy period.…”

Section: Introductionmentioning

confidence: 99%

Hydromechanical behaviour of a silty sand from a steep slope triggered by artificial rainfall: from unsaturated to saturated conditions

2013

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This paper presents an experimental investigation aimed at studying the hydromechanical behaviour of a silty sand from a steep slope in Ruedlingen in the northeast of Switzerland, where a landslide-triggering experiment was carried out. The hydromechanical behaviour of the statically compacted Ruedlingen silty sand has been studied under saturated and unsaturated conditions, beginning with different initial void ratios and water contents. The specimens were prepared in the laboratory using static compaction, to reproduce the mean dry density and mean water content expected in natural unsaturated in situ conditions, thus promoting specimen homogeneity and test repeatability. The choice of compaction parameters was supported by a detailed physical and microstructural investigation to produce laboratory specimens with a similar microstructure to that of the natural soil. The aim of the work was to characterize the mechanical behaviour of the soil at different gravimetric water contents in a triaxial stress path apparatus and to link the mechanical behaviour with the soil-water retention curve obtained under suction-controlled conditions with different void ratios. Soil specimens with three different gravimetric water contents were exposed to conventional isotropically consolidated drained and undrained stress paths for the water phase and to stress paths simulating in situ anisotropic compression followed by a decrease of mean effective stress at constant axial load. The radial deformation of the unsaturated specimens was measured with a laser device installed in a triaxial stress path cell. Results have been interpreted using a Bishop stress approach, evaluating the suction through the water retention curve. A simple equation has been proposed to model the compressibility behaviour of the soil tested, which depends on the parameter and the stress ratio . Possible unstable response along the stress path analysed has been investigated by means of second-order work and the validity of a unified framework has also been verified under unsaturated conditions. Key words: unsaturated soil, shallow landslide, water retention curve, instability, triaxial stress path tests. Résumé :Cet article présente une étude expérimentale visant à étudier le comportement hydromécanique d'un sable silteux provenant d'une pente raide à Ruedlingen dans le nord-est de la Suisse, où un essai de glissement de terrain provoqué a été réalisé. Le comportement hydromécanique du sable silteux de Ruedlingen, compacté statiquement, a été étudié en conditions saturées et non saturées, en débutant avec différents indices des vides et teneurs en eau initiaux. Les échantillons ont été préparés au laboratoire par compaction statique afin de reproduire la densité sèche moyenne et la teneur en eau moyenne réalistes dans des conditions naturelles in situ, et de favoriser l'homogénéité des échantillons et la reproductibilité des essais. Le choix des paramètres de compaction s'est fait selon une étude détaillée des paramètres physiques et microstruct...

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“…The latter approach has been widely adopted recently both in the analysis of the incremental response of soil elements (see, e.g. [38]) and in the context of slope stability (e.g., [39,40]). The role of time dependency of the mechanical behaviour, that would discriminate between unstable, temporary unstable and stable responses of frictional materials, has been discussed by di Prisco et al [34].…”

Section: Failure Initiationmentioning

confidence: 99%

A laboratory investigation on an undisturbed silty sand from a slope prone to landsliding

2010

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A laboratory investigation is presented for undisturbed samples of a silty sand under saturated conditions. The soil was sampled from test pits south of Rüdlingen in North-East Switzerland, where a landslide triggering experiment was carried out on a steep forest slope. The aim of the work was to characterise the behaviour of the soil in triaxial tests, in the light of the possible failure mechanisms of the slope. Conventional drained and undrained triaxial tests were conducted to detect critical state conditions as well as peak shear strength as a function of confining pressure. Soil specimens were also exposed to stress paths simulating in situ water pressure increase to study the stress-strain response and to enhance the ability to predict failure conditions more accurately in the future. Possible unstable response along the stress paths analysed was investigated by means of second order work and strain acceleration. The results show that temporary unstable conditions may be encountered for this soil at stress ratios below ultimate failure and even below critical state line, depending on void ratio, drainage conditions and time dependent compressibility. A modified state parameter is explored as a potentially useful tool to discriminate conditions leading to eventual collapse.

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Hydro-mechanical modelling of landslides with a material instability criterion

Cited by 52 publications

References 27 publications

Bifurcation modeling in geomaterials: From the second‐order work criterion to spectral analyses

Bifurcation modeling in geomaterials: From the second‐order work criterion to spectral analyses

Hydromechanical behaviour of a silty sand from a steep slope triggered by artificial rainfall: from unsaturated to saturated conditions

A laboratory investigation on an undisturbed silty sand from a slope prone to landsliding

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