Analysis of a retrogressive landslide in glaciolacustrine varved clay

The largest landslides in Estonia are associated with glaciolacustrine varved clays. One of the recent slope failures, Audru landslide, was chosen for detailed investigation. Landslide morphology was instrumentally measured and the underlying geological setting investigated with eight boreholes penetrating the varved clay. Varve correlation was used to localize the failure zone and estimate the extent of the displaced material within the landslide body. Field measurements and limit equilibrium models displayed a retrogressive complex of three separate sliding events. The first stage of Audru landslide was initiated by the river undercutting and was followed by retrogressive slides that caused partial liquefaction of the landslide body. The influence of the various modeling parameters on the overall slope stability was also investigated.

Research Highlights
► Detailed survey of the retrogressive landslide
► Varve correlation used to picture changes within the landslide
► Slope stability analysis to understand the mechanism and the influence of the various parameters