ISSN: 0149-6115
Published Online: 22 May 2007
Page Count: 5

A Numerical View into Direct Shear Specimen Size Effects

Jacobson, Douglas E.
Graduate Research Assistant and Assistant Professor, respectively,Department of Civil and Environmental Engineering, San Diego State University,CA,

Valdes, Julio R.
Graduate Research Assistant and Assistant Professor, respectively,Department of Civil and Environmental Engineering, San Diego State University,CA,

Evans, T. Matthew
Assistant Professor,Department of Civil, Construction, and Environmental Engineering, North Carolina State University,NC,

(Received 21 November 2006; accepted 19 March 2007)

Abstract

The ASTM D 3080-04 standard, Standard Test Method for Direct Shear Test of Soils under Consolidated Drained Conditions, indicates that the direct shear test specimen width L must be at least ten times larger than the largest particle in the specimen, L/d ≥ 10. The results documented in this note provide visual insight into specimen size and boundary effects through discrete element simulations conducted with numerical specimens ranging in size from L/d = 6.5 to L/d = 177. Particle translation data indicate that in the tested configuration, localized shear zones located far from the specimen boundaries develop only when the specimen size is L/d > 58. The results provide a description of the microstructure evolution during shearing and suggest that the ASTM specimen size criterion may be inappropriate when localized shear banding in uniform granular materials is sought.

Keywords:
DEM, direct shear, localization, scale effects

Paper ID: GTJ100923
DOI: 10.1520/GTJ100923
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