Numerical investigations of retrogressive failure in sensitive clays: revisiting 1994 Sainte-Monique slide, Quebec
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Numerical investigations of retrogressive failure in sensitive clays: revisiting 1994 Sainte-Monique slide, Quebec
Abstract Retrogressive slope failure is ubiquitous in regions of abundant sensitive clays with its mechanism yet to be understood comprehensively. This study gives numerical investigations of retrogressive slope failure with a focus on the 1994 SainteMonique slide, Quebec, using a large deformation finite element method. Failure mechanisms and post-failure behaviours including the global kinematics and retrogression distance are highlighted with controlling factors discussed in parametric studies. Key features of post-failure behaviours of the 1994 Sainte-Monique slide are reproduced with the configuration of sliding mass deposits comparable to the site investigations. Post-failure kinematics and retrogression distance are sensitive to sensitivity, brittleness and viscosity of soils and riverbed geometry. Parametric studies may contribute to assess potential retrogression recurrence in the region and its retrogression distance upon current set of in situ parameters. Keywords Slides . Retrogressive failure . Sensitive clays . Shear band . Large deformation numerical modelling Introduction Many natural clays undergo strain softening during shearing, characterised by distinct peak and residual shear strengths and usually termed as sensitive clays. In northern countries, such as Norway and Canada, sensitivity of the so-called quick clays can be as high as over 100 (Crawford 1968; Lundstrom et al. 2009; Quinn et al. 2011; Gylland et al. 2013), and thus, slope failure is ubiquitous in those regions (Skempton 1964, 1985; Kerr and Drew 1968; Gregersen and Loken 1979; Solberg et al. 2008). Loss of shear strength during shearing can cause rapid escalation of the slide scale with progressive failure (Bernander 2000; Puzrin et al. 2004; Puzrin and Germanovich 2005; Andresen and Jostad 2007; Zhang et al. 2015; Buss et al. 2019). A particular form of failure, which has been received considerable attention recently, is the retrogressive spreading failure with an uphill shear band propagation due to removal of downslope support (Quinn et al. 2011, 2012; Locat et al. 2011, 2013; Dey et al. 2016; Zhang et al. 2019b). Such phenomena occur in nature and are attributable to, for example, the erosion of riverbank and steep cut. The 1994 Sainte-Monique slide in Quebec, Canada, is a typical example initiated by riverbank erosion (Locat et al. 2015; Tran and Solowski 2019). Initiation mechanisms and criteria for such progressive failure in sensitive soils have been well understood during the last decade (Puzrin et al. 2004; Puzrin and Germanovich 2005; Quinn et al. 2012; Zhang et al. 2015, 2017). This study seeks to numerically explore the post-failure behaviours of the Sainte-Monique slide shedding light on the kinematics of debris flow and retrogression distance which are keys for risk assessment.
The 1994 Sainte-Monique slide The Sainte-Monique slide occurred along a brook in Quebec on 21st April 1994 (Locat et al. 2015).
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