Centrifuge modelling of a roto-translational landslide in stiff clay formation

Roto-translational landslides are characterized by two movement types at different landslide parts, i.e., rotational movement at the headscarp and translational movement at the toe. They are widely distributed in clay formations with planar or subhorizontal layers, posing threats to human life and infrastructure. Due to the different shapes of the sliding surfaces, the kinematics of roto-translational landslides show complicated patterns with varying spatial and temporal distributions. Forecasting the rapid sliding of roto-translational landslides presents challenges, as they often manifest as unnoticed slowly movement. The sliding surfaces of the roto-translational landslides feature concave-upward shape at the landslide head and a planar shape at the landslide accumulation zone, leading to complex deformation mechanisms. Roto-translational landslides usually exhibit creep deformation along sliding surfaces, showing transverse cracks on the ground surfaces. However, the scarcity of experimental data has significantly hindered a deep understanding of their failure mechanisms. Our research probes into the rotational failure phenomena of landslides in stiff clay formations, utilizing geotechnical centrifuge modelling and laboratory creep tests. Our findings reveal that rotational failures in model slopes are exclusively triggered under conditions of an undrained boundary at the basal shear zone. The post-failure behaviour is characterized by a settlement at the slope crest and a pronounced bulge at the toe, resulting in complex rotational movements along the basal sliding surface. Moreover, our laboratory experiments illuminate the creep behaviour of shear-zone materials under undrained conditions. In particular, samples with a high initial water content under sustained loading are highly susceptible to a quick transition into tertiary creep, leading to accelerated failure. These experimental insights substantially advance our understanding of the rotational failure patterns observed in clay-based landslides.