How does anisotropy control rock slope deformation? A discrete element modelling investigation

&amp;lt;p&amp;gt;Deep-seated failures of rock slopes are partly controlled by structural, lithological and topographical factors. Among structural factors, layering, schistosity and foliation in rock material, which could be described as inherent anisotropy of the material, affect initiation and evolution of deep-seated rock slope &amp;lt;span&amp;gt;deformation&amp;lt;/span&amp;gt;, especially in slow moving landslides.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;In order to document such an influence of material anisotropy on slope stability, we carry out a parametric study using discrete element modelling (DEM). After a validation exercise for fully isotropic material, where we compare our numerical approach to an analytical slope stability solution, we introduce anisotropy (transverse isotropy) in our DEM model by inserting preferentially oriented and weakened bonds between discrete elements (weakness plane) to simulate two typical transverse isotropic lithologies, claystone and gneiss respectively. Considering these two lithologies, we then explore the influence of the weakness plane&amp;amp;#8217;s orientation with respect to the slope angle for both ridge and valley geometries.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We show that certain orientations of the weakness plane relative to the topographic slope favour deep-seated deformation. We also observe significant disparities in failure initiation, failure surface localisation, and mobilized volume depending on the &amp;lt;span&amp;gt;weakness plane&amp;lt;/span&amp;gt; orientation. For instance, most unstable slopes occur when the weakness plane rises 10&amp;amp;#176; to 30&amp;amp;#176; less than the hillslope angle. These instabilities are associated with well-localized deformation at depth that when intersecting the surface mimic some of the morphological features (such as counter-slope scarps) that are commonly described along mountain ridges in association with &amp;lt;span&amp;gt;slow-moving and deep-seated rock slope failures&amp;lt;/span&amp;gt;.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Our results help explain the appearance or absence of deep-seated failure in mountainous areas and allow to better assess slope failure hazard induced by anisotropic rock strength.&amp;lt;/p&amp;gt;</jats:p

Intensity and volumetric characterizations of hydraulically driven fractures by hydro-mechanical simulations

International audienc

Transport and deposition of weakly inertial particles in closed channel flows at low Reynolds number

International audienc

Effects of Suffusion on the Soil’s Mechanical Behavior: Experimental Investigations

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Evolution of the incidence of hepatitis B virus infection and immunization rates in a large French cohort born between 1960 and 1994

International audienceIn France, several successive changes in anti-hepatitis B virus (HBV) vaccination policies occurred since 1982. We estimated the incidence and prevalence of HBV infection according to years of birth 1960 to 1994 in a large sentinel cohort to evaluate the epidemiology of HBV during vaccination policy changes. A retrospective cohort study included data from all HIV, HBV and hepatitis C virus (HCV) screening facilities in Grand Lyon. From 2005 to 2010, all 57113 individuals with complete HBV serologic status were enrolled. Survival analyses modeled separately various ages in each birth cohort. The proportion of immunized individuals increased in birth cohorts 1978 to 1984 (up to 58.3% (95% confidence interval (CI), 43.3-68.2 at age 15). In post-1985 birth cohorts, this proportion decreased to 19.5% (95% CI, 15.5-24) in birth cohort 1987 at age 15. Probability of past or current HBV infection increased constantly in birth cohorts 1960 to 1967, up to 12% (95% CI, 10.4-14) at age 30, then decreased gradually in birth cohorts 1968 to 1991, down to 0.9% (95% CI, 0.7-1.2) at age 17.5. In post-1991 cohorts, the probability of HBV infection increased again, up to 2.5% (95% CI, 1.7-3.6) at age 17.5. HBV incidence fluctuated between 5 and 8 per 1000 person-years in pre-1986 birth cohorts, decreased to 2.1 (95% CI, 1.5-2.7) in birth cohorts 1986 to 1991 but rebounded to 5 (95% CI, 3.5-7.1) in post-1991 birth cohorts. HBV incidence was remarkably high in young adults with noticeable variations concomitantly to vaccination policy changes. A dramatic decline in immunization rate was temporally associated with a sharp rebound of infection after withdrawal of systematic adolescent vaccination in 1998