The University of Massachusetts Amherst
University of Massachusetts Amherst

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Effect of nonuniform stresses on measured DSS stress‐strain behavior

TitleEffect of nonuniform stresses on measured DSS stress‐strain behavior
Publication TypeJournal Article
Year of Publication1994
AuthorsDegroot DJ, Germaine JT, Ladd CC
JournalJournal of Geotechnical Engineering
Start Page892
Date Published05/1994
KeywordsEquipment and machinery, Shear resistance, Shear stress, Soil properties, Strain hardening and softening, Stress strain relations, Vertical loads

This paper presents results of a laboratory investigation of the influence of the nonuniform stresses imposed by the Geonor direct simple‐shear (DSS) apparatus on measured stress‐strain behavior. The investigation concentrated on the influence of the apparatus on the measured strain‐softening behavior of cohesive soils during constant volume (undrained) shear. Special DSS tests were conducted on an elastic material and cohesive soils at varying overconsolidation ratios. The experimental results clearly indicate that the non-uniformity of stresses imposed by the device during undrained shear causes a decrease in the vertical effective stress with increasing shear strain. This in turn causes a reduction in the measured horizontal shear resistance at large strains. The device‐induced “unloading” probably has relatively little effect on measured peak strengths in K0 consolidated‐undrained DSS tests but certainly contributes to the pronounced strain softening typically observed.