How Stable Is the Nice Slope? – An Analysis Based on Strength and Cohesion from Ring Shear Experiments
The upper shelf of the landslide-prone Ligurian Margin (Western Mediterranean Sea) off Nice well-known for the 1979 Airport Landslide is a natural laboratory to study preconditioning factors and trigger mechanisms for submarine landslides. For this study low-stress ring shear experiments have been carried out on a variety of sediments from >50 gravity cores to characterise the velocity-dependent frictional behaviour. Mean values of the peak coefficient of friction vary from 0.46 for clay-dominated samples (53 % clay, 46 % silt, 1 %) sand up to 0.76 for coarse-grained sediments (26 % clay, 57 % silt, 17 % sand). The majority of the sediments tested show velocity strengthening regardless of the grain size distribution. For clayey sediments the peak and residual cohesive strength increases with increasing normal stress, with values from 1.3 to 10.6 kPa and up to 25 % of all strength supported by cohesive forces in the shallowmost samples. A pseudo-static slope stability analysis reveals that the different lithologies (even clay-rich material with clay content ≥50 %) tested are stable up to slope angles <26° under quasi-drained conditions.
KeywordsRing shear Submarine landslide Slope stability analysis
We are grateful to Mary Belke-Brea for help with grain size analysis and Gauvain Wiemer and Alois Steiner for assistance in the geotechnical laboratory. We thank both referees Marten Vanneste and Demian Saffer for constructive criticism. The study was funded by DFG via MARUM Cluster of Excellence.
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