Static and Cyclic Shear Strength of Cohesive and Non-cohesive Sediments

摘要

Submarine slope failures are common along tectonically and seismically active margins and may have devastating impact on onshore and offshore infrastructure as well as coastal communities. Soils show a variable response to periodic loading compared to static loading - making static and cyclic loading experiments compulsory for submarine slope stability and mass-movement initiation studies. Results from (i) a generic study investigating the shear strength of water-saturated sediments upon drained static vs. undrained cyclic loading, and from (ii) a comparison to natural samples are presented. A direct shear apparatus and the MARUM Dynamic Triaxial Testing Device have been used to compare undrained, cyclic to drained, static shear strengths of reconstituted samples with different clay to quartz (sandy silt) ratios. With this experimental set-up we aim to identify the failure potential of cohesive to granular material under cyclic and static loading condition. Results indicate that the cyclic shear strengths of material mixtures with less than 20% clay mineral content are significantly lower than their static shear strengths. Mixtures with a clay mineral content exceeding 20% show converging cyclic, undrained and static, drained shear strengths. Ongoing studies build on the knowledge gained from the generic endmember tests and integrate natural samples from the Nankai Trough accretionary wedge (Japan).