Location
San Diego, California
Presentation Date
26 May 2010, 4:45 pm - 6:45 pm
Abstract
Cyclic threshold shear strain, γt, is small cyclic shear strain amplitude above which soil properties significantly change with the number of cycles, N, and below which such changes are for all practical purposes negligible. To date, three cyclic threshold shear strains have been experimentally verified: for cyclic settlement (cyclic compression), for residual cyclic pore water pressure, and for cyclic stiffening. Subject of the paper is testing of fourth cyclic threshold shear strain for cyclic degradation, γtd. When fully saturated soil is subjected in undrained conditions to moderate or large cyclic strain-controlled loading, its secant shear modulus, Gs, decreases with N. This is quantified for given cyclic shear strain amplitude, γc, by degradation index, δ = GsN /Gs1, where GsN = Gs at cycle N. Index δ and N are related via degradation parameter t = −(logδ / logN) which measures the rate of cyclic degradation. At γc < γtd there is no cyclic degradation and t = 0. If γc > γtd cyclic degradation takes place and t > 0. With a special simple shear device for small-strain testing the variation of t with γc was examined and γtd evaluated for three clayey soils. Results show that γtd increases with plasticity index, PI. For PI=12 γtd=0.015%, for PI=26 γtd=0.04, and for PI=47 clay γtd=0.05%. Testing procedure and comparison to other types of γt are presented.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
5th International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics
Publisher
Missouri University of Science and Technology
Document Version
Final Version
Rights
© 2010 Missouri University of Science and Technology, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Tabata, Kentaro and Vucetic, Mladen, "Threshold Shear Strain for Cyclic Degradation of Three Clays" (2010). International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. 30.
https://scholarsmine.mst.edu/icrageesd/05icrageesd/session01/30
Included in
Threshold Shear Strain for Cyclic Degradation of Three Clays
San Diego, California
Cyclic threshold shear strain, γt, is small cyclic shear strain amplitude above which soil properties significantly change with the number of cycles, N, and below which such changes are for all practical purposes negligible. To date, three cyclic threshold shear strains have been experimentally verified: for cyclic settlement (cyclic compression), for residual cyclic pore water pressure, and for cyclic stiffening. Subject of the paper is testing of fourth cyclic threshold shear strain for cyclic degradation, γtd. When fully saturated soil is subjected in undrained conditions to moderate or large cyclic strain-controlled loading, its secant shear modulus, Gs, decreases with N. This is quantified for given cyclic shear strain amplitude, γc, by degradation index, δ = GsN /Gs1, where GsN = Gs at cycle N. Index δ and N are related via degradation parameter t = −(logδ / logN) which measures the rate of cyclic degradation. At γc < γtd there is no cyclic degradation and t = 0. If γc > γtd cyclic degradation takes place and t > 0. With a special simple shear device for small-strain testing the variation of t with γc was examined and γtd evaluated for three clayey soils. Results show that γtd increases with plasticity index, PI. For PI=12 γtd=0.015%, for PI=26 γtd=0.04, and for PI=47 clay γtd=0.05%. Testing procedure and comparison to other types of γt are presented.
