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Landslides involving sensitive clays are recurrent events in the world's northern regions and are especially notorious in eastern Canada. The two critical factors that separate sensitive clay landslides from traditional slope stability analysis are the highly brittle behavior in undrained conditions (strain-softening) characteristic of progressive or retrogressive failures and the large deformations associated with them. Conventional limit equilibrium analysis has numerous shortcomings in incorporating these characteristics when assessing landslides in sensitive clays. This paper presents an extensive literature review of the failure mechanics characteristics of landslides in sensitive clays and the existing constitutive models and numerical tools to analyze such slopes' stability and post-failure behavior. The advantages and shortcomings of the different techniques to incorporate strain-softening and large deformation in the numerical modeling of sensitive clay landslides are assessed. The literature review depicts that elastoviscoplastic soil models with non-linear strain-softening laws and rate effects represent the material behavior of sensitive clays. Though several numerical models have been proposed to analyze post-failure runouts, the amount of work performed in line with sensitive clay landslides is very scarce. That creates an urgent need to apply and further develop advanced numerical tools for better understanding and predicting these catastrophic events. [ABSTRACT FROM AUTHOR]

This paper presents a geotechnical study of a Champlain Sea clay landslide at Breckenridge, Quebec, Canada. Previous studies have interpreted the landslide as triggered by an earthquake occurred about 1020 cal years BP. The current study is to estimate the minimum ground acceleration required to trigger the landslide as part of an effort to further understand the earthquake. The study consists of field and laboratory testing and slope stability analysis. Considerable evidences are presented to understand the slope failure mechanism. The result indicates a minimum horizontal ground acceleration of 0.28 g occurred at the site. Most importantly, the paper provides a case history for better understanding landslide hazards associated with sensitive clay failures in the region. Particularly, the study finds that the landslide is a "flake" type failure as opposed to a retrogressive failure commonly perceived for Champlain Sea clay landslides. It brings to light the "flake" slide as an important factor to consider for improvement of the current predictive models for sensitive clay failures. It also shows that earthquake-triggered "flake" slide can be much larger than retrogressive failures in the same settings. The case history may therefore help as a reference for improved mitigative measures. [ABSTRACT FROM AUTHOR]

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Anisotropic behaviour of the clay core, blanket, and foundation of aging water retaining earth fill dams on glacio-lacustrine clay deposits in Canada may be a result of environmental loading. The repeated wetting-drying and freezing-thawing cycles produce fissures that can cause degradation of strength with time. Undisturbed clay samples taken from field investigations of an existing aging water retaining earth fill dam were tested in the laboratory to obtain the parameters used in the numerical modeling. A testing program was implemented in order to determine the basic soil properties along with mineralogy, strength, and deformation characteristics of the collected clay samples. Laboratory tests include index property tests, Scanning Electron Microscopy (SEM) tests, X-Ray Diffraction (XRD) tests, one-dimensional consolidation oedometer tests, consolidated drained direct shear tests, and isotropically consolidated undrained triaxial compression tests. Results revealed that the clay samples from the clay core, blanket and foundation were similar in terms of structural and mineralogical composition. The observed interlayered smectite and illite indicated that the micro fabric was anisotropic. Strength anisotropy was noticed as results had different cross shear and horizontal shear strength values. Numerical modeling was performed to assess the slope stability of an aging earth dam that experienced sliding movements using parameters from the completed laboratory investigation. Findings from slope stability analyses indicated that a better representation of the observed site conditions was evident when strength anisotropy was considered. [ABSTRACT FROM AUTHOR]