Borehole Shear Test and Slope Stability

by Richard L. Handy, Iowa State Univ, Ames, IA, USA,

Document Type: Proceeding Paper

Part of: Use of In Situ Tests in Geotechnical Engineering


Three Iowa landslides analyzed on the basis of Borehole Shear Test (BST) data are reported. The soils included CL and ML loess and glacial till, and CH clay shale. Back-calculations from BST friction angles measured in the shear zones consistently indicated that cohesion after sliding is near zero, suggesting that after-slip equilibrium must derive mainly from internal friction in the shear zone. Stage BST's were performed on a 28-ft high lagoon embankment of compacted CH soil over random fill, to determine if the lagoon could be safely put into service. Fourteen BST shear envelopes were obtained in two days and gave sufficient data for probabilistic determinations of the failure risk based both on the range in individual strengths and the range in predicted means study results are presented.

Subject Headings: Shear tests | Boring | Slope stability | Shear stress | Shear failures | Shear strength | Landslides | Failure analysis | Iowa | United States

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