Because the direct simple shear (DSS) mode is recognized as the most representative failure condition along a sliding surface, a DSS testing system capable of testing large soil particles is useful to determine the strength parameters of gravelly soils. In DSS tests, the size and boundary effects are two crucial factors that affect the consistency of the test results. To evaluate the size and boundary effects in DSS conditions, numerical experiments using the distinct element method are performed to investigate the influences of specimen dimensions on the macroscopic stress-strain relationship and microscopic uniformity in terms of the specimen diameter (D), specimen height (H), and maximum particle size (dmax). The size effect is evaluated on the variations of stress-strain curves with the specimen dimensions and dmax. The boundary effect is assessed in terms of the spatial distribution of the particle displacement and contact force fields. The results show that: 1. the boundary effect can be reduced effectively when H/D decreases, 2. the difference in boundary effect is insignificant between Cambridge and Norwegian Geotechnical Institute types of simple shear configurations, and 3. there is a relatively consistent stress-strain relationship when H/dmax is no less than 7.
All Science Journal Classification (ASJC) codes
- Geotechnical Engineering and Engineering Geology