Geotechnical characterization and stability analysis of subaqueous slopes in Lake Lucerne (Switzerland)

Anastasiia Shynkarenko; Katrina Kremer; Sylvia Stegmann; Paolo Bergamo; Agostiny Marrios Lontsi; Alexander Roesner; Steffen Hammerschmidt; Achim Kopf; Donat Fäh

doi:10.1007/s11069-022-05310-1

Geotechnical characterization and stability analysis of subaqueous slopes in Lake Lucerne (Switzerland)

Nat Hazards (Dordr). 2022;113(1):475-505. doi: 10.1007/s11069-022-05310-1. Epub 2022 Mar 29.

Authors

Anastasiia Shynkarenko¹, Katrina Kremer^{1

2}, Sylvia Stegmann³, Paolo Bergamo¹, Agostiny Marrios Lontsi¹, Alexander Roesner³, Steffen Hammerschmidt³, Achim Kopf³, Donat Fäh¹

Affiliations

¹ Swiss Seismological Service (SED), ETH Zürich, Sonneggstrasse 5, 8092 Zurich, Switzerland.
² Geological Institute and Oeschger Centre for Climate Change Research, University of Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland.
³ MARUM-Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse 8, 28359 Bremen, Germany.

Abstract

Tsunamis occur not only in marine settings but also in lacustrine environments. Most of the lacustrine tsunamis are caused by seismically- or aseismically-triggered mass movements. Therefore, an assessment of the stability of subaqueous slopes is crucial for tsunami hazard assessment in a lake. We selected Lake Lucerne (Switzerland) as a natural laboratory to perform an in-depth geotechnical characterization of its subaqueous slopes. This lake experienced documented tsunamis in 1601 and 1687. Some of its slopes still bear sediment volumes with a potential for tsunamigenic failure. To identify such slopes, we interpreted available reflection seismic data and analyzed the bathymetric map. Then, we performed 152 dynamic Cone Penetration Tests with pore pressure measurement (CPTu) and retrieved 49 sediment cores at different locations in the lake. These data were used to characterize the failure-prone sediments and to evaluate the present-day static stability of subaqueous slopes. Obtained results allowed the definition of three classes of slopes in terms of static stability: unstable slopes, stable slopes close to the unstable state, and stable areas. Non-deltaic slopes with thicker unconsolidated fine-grained sediment drape and moderate-to-high slope gradients (> 5-10°) have the lowest Factor of Safety. In agreement with previous studies, the failure plane for the non-deltaic slopes is embedded within the fine-grained glaciolacustrine sediments. Deltaic slopes with prevailing coarse-grained sediments mostly appear statically stable. Finally, we generalized the measured undrained shear strength profiles $s_{u} (z)$ into the depth-dependent power-law models. These models define the $s_{u}$ of Lake Lucerne's sediments and can be applied to other lakes with similar sedimentation history.

Supplementary information: The online version contains supplementary material available at 10.1007/s11069-022-05310-1.

Keywords: Cone penetration testing; Lake Lucerne; Sediment coring; Slope stability; Subaqueous landslides; Undrained shear strength.