In this study, we performed 26 undrained triaxial compression and 32 constant-volume ring shear tests on two clean sands and one silty sand. We then used these results to evaluate the critical states, and shear strength ratios mobilized at yield and at critical state. We obtained yield strength ratios that ranged from 0.16 to 0.32 and from 0.20 to 0.35 in triaxial compression and ring shear, respectively. Critical strength ratios mobilized prior to particle damage ranged from 0.01 to 0.26 in triaxial compression and from 0.04 to 0.22 in ring shear. Particle damage and shear displacement increased the slopes of the critical-state lines during ring shear testing, and consequently the critical strength ratios incorporating particle damage decreased from 0.02 to 0.12. In addition, specimen brittleness (before particle damage) increases with initial void ratio and state parameter and is affected by initial fabric and particle shape. However, particle damage and crushing considerably increases sand brittleness, making it essentially independent of initial void ratio. A unique relation is found between sand brittleness and critical strength ratio independent of sand type, mode of shear, fabric, and particle damage, which indicates an upper bound critical strength ratio of about 0.3 for mildly contractive sands.
- Critical state
- Particle damage
- Ring shear tests
- Undrained shear strength
ASJC Scopus subject areas
- Civil and Structural Engineering
- Geotechnical Engineering and Engineering Geology