# TXT-tool 3.001-1.3: Laboratory Measurement of Fully Softened Shear Strength and Its Application for Landslide Analysis

## Abstract

Fully softened shear strength is equivalent to the peak shear strength of remolded soil specimens. Fully softened shear strength is important when evaluating the stability of first time slides and compacted fills. It is generally measured using various soil testing methods such as direct shear, direct simple shear, triaxial or ring shear tests. However, as the direct shear test devices are readily available in many geotechnical engineering laboratories, it is recommended to use this device to measure the fully softened shear strength. Generally, the fully softened shear envelopes are curved, starting from origin. Therefore, using constant volume direct simple shear devices are recommended to obtain the fully softened shear envelopes in order to accurately capture this curvature. This tool explains the importance of fully softened shear strength for slope stability analysis, methods used to measure the fully softened shear strengths in laboratory, and available correlations to estimate the fully softened shear strength with index properties.

## Keywords

Fully softened shear strength Direct shear test Slope stability Plasticity index Liquid limit## Notes

### Acknowledgements

The authors would like to acknowledge the support of California State University Fullerton through intramural grant to conduct laboratory experiments pertinent to this research.

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