Effect of Specimen Size and Boundaries on the Results of Direct Simple Shear Tests
Publication: Geo-Congress 2024
ABSTRACT
Direct simple shear (DSS) tests are widely used to capture the shearing behavior of soils. A major concern with a DSS test is the non-uniform distributions of stress and strain on the horizontal platens of this device. A series of DSS simulations were carried out in this study using 3D discrete element analysis (DEM) to examine the effects of specimen size and boundary conditions. The gradation of a coarse sand was used to generate different sphere sizes, which were then uniformly spread throughout the model. While smooth lateral walls were used, the horizontal boundaries had a high coefficient of friction to minimize slippage. A constant-volume condition was imposed by controlling boundary displacements. Different specimen diameters were modeled to examine the effect of diameter-to-height ratio (D/H) on stress path, peak shear stress, and post peak behavior. Numerical simulations indicated that boundary effects became more prominent at higher consolidation stresses for a given D/H. Such boundary effects were, however, reduced by enlarging the sample diameter (i.e., raising D/H). Specimen boundary effects were minimized in specimens with a D/H ≥ 2.8, resulting in the same shearing behavior as those with larger D/H ratios.
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Published online: Feb 22, 2024
ASCE Technical Topics:
- Boundary shear
- Discrete element method
- Domain boundary
- Engineering fundamentals
- Flow (fluid dynamics)
- Fluid dynamics
- Fluid mechanics
- Geomechanics
- Geotechnical engineering
- Hydrologic engineering
- Laboratory tests
- Mathematics
- Methodology (by type)
- Numerical methods
- Shear stress
- Shear tests
- Soil mechanics
- Soil properties
- Soil tests
- Stress (by type)
- Stress distribution
- Structural analysis
- Structural engineering
- Tests (by type)
- Water and water resources
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