Shear strength, interparticle locking, and dilatancy of granular materials

• Published in: Canadian geotechnical journal Vol. 44; no. 5; pp. 579 - 591
• Main Authors: Guo, Peijun, Su, Xubin
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.05.2007; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Engineering geology; Exact sciences and technology; Friction; Geotechnology; Grain size; Granular materials; Laboratory tests; Limestone; Measurement; Mechanical properties; Sand; Sand & gravel; Shear (Mechanics); Shear strength; Soil mechanics; Stress-strain curves; Canada; stress; shear strength; sand; dilation; dilatancy; shear; standard samples; granular materials; pressure; particles; oxygen; friction
• ISSN: 0008-3674; 1208-6010
• DOI: 10.1139/t07-010

The effect of particle angularity on the strength and dilation of granular materials is investigated through a series of laboratory tests on two materials, Ottawa standard sand (Sand O) and crushed limestone (Sand L), that are made up of rounded and angular particles, respectively. Triaxial tests on both materials at different confining pressures and initial void ratios show that particle angularity has a substantial effect on both the peak friction angle φϕ p and the mobilized friction angle at the onset of dilation, φϕ f . It is found that φϕ f is smaller than the critical friction angle φϕ cv for Ottawa sand; nevertheless φϕ f is larger than φϕ cv for Sand L owing to interparticle locking induced by particle angularity. The experimental results clearly show the contributions to shear resistance from both dilation and interlocking, with interlocking still largely existing at the peak stress ratio but not at the critical state. Suggestions are made to modify the stress-dilatancy formulations for sand to take into account the effect of interparticle locking associated with particle angularity.Key words: granular material, dilatancy, interlocking, and particle shape.