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Shear Strength Gantry with Automated Vane Shear (AVS)

Overview

Thumbnail image of Shear Strength Gantry with Automated Vane Shear (AVS) Shear strength in sediments is the maximum resistance of a material to deformation by shear stress and can be measured by an automated vane shear instrument. Shear strength is a way to measure slope stability as it relates to friction, particle interlocking, and cohesion. The automated vane shear is suitable for sediment not affected by cementation (e.g., saturated, clay-rich, soft sediment).

Note: The AVS instrument is not in continuous operation and is available by request.

Instrument Make and Model

GEISA FL2 SS

Estimated Measurement Time

  • Sample Measurement: ~5 mins/measurement

Quantity of Sample Material

~5 or 10 cm whole round or split-core surface; >80 cm3 of material

Principles & Analytical Capabilities

The Giesa AVS system is suited for measuring the shear strength of very soft to relatively stiff marine sediments and is especially useful for analyzing undisturbed clay- or silt-rich samples. The system consists of a controller and a gantry for shear vane insertion. A four-bladed vane is pushed carefully into a sediment sample until the top of the vane is level with the surface of the sample. There are 6 sizes of vane blades available. The vane is rotated to determine the torque required to cause the material to shear (failure torque). Failure torque is determined by measuring the rotation of a torsional spring using a spring-specific relation between rotation angle and torque.

Data Generated

Data components:

  • Angle of shear (deg): internal angle of friction; stress-dependent component
  • Torque (Nm): resistance of cohesion and internal friction
  • Vane shear strength (N/m2): strength value at the failure point of the sample, determined by maximum torque (Nm) divided by the vane constant (m3)
  • Max torque angle (deg): angle at which maximum torque is reached
  • Penetration direction: orientation of penetration (orthogonal to the shear experiment plane). Values include "X", "Y", "Z", or "–Z"
  • Vane rotation rate (deg/s): rate of rotation for automated vane measurement

Data files:

  • Automated vane shear (CSV): tabular file of automated vane shear results

Data Example

Graph of [copy from caption].
Shear strength data from Hole U1558F of IODP Expedition 393 in the central South Atlantic Ocean.1

Procedures & Manuals

References

1  Coggon, R. M., Teagle, D. A. H., Sylvan, J. B., Reece, J., Estes, E. R., Williams, T. J., Aizawa, M., Albers, E., Amadori, C., Belgrano, T. M., Borrelli, C., Bridges, J. D., Carter, E. J., Christeson, G. L., D'Angelo, T., Dinarès-Turell, J., Doi, N., Estep, J. D., Evans, A., … Zhang, G. (2024). IODP Expedition 393 Vane shear strength (AVS) [Data set]. International Ocean Discovery Program. https://doi.org/10.5281/zenodo.10672660