For saturated medium to dense sand subjected to shear, when the deviatoric stress ratio approaches its limit (on the failure surface in stress space), the stress ratio is essentially kept constant but, accompanying the development of an excessive deviatoric strain, the deviatoric stress as well as the hydrostatic stress continuously increases. This phenomenon is termed as dilative hardening. In this study the dilative hardening responses of the Tung Chung sand and the UST sand were experimentally investigated. The experimental results from a series of monotonic triaxial compression tests under both undrained and drained conditions clearly indicated that there exists a critical state line that defines the void ratios (e) and the associated effective mean normal stresses (p') at critical...[ Read more ]

For saturated medium to dense sand subjected to shear, when the deviatoric stress ratio approaches its limit (on the failure surface in stress space), the stress ratio is essentially kept constant but, accompanying the development of an excessive deviatoric strain, the deviatoric stress as well as the hydrostatic stress continuously increases. This phenomenon is termed as dilative hardening. In this study the dilative hardening responses of the Tung Chung sand and the UST sand were experimentally investigated. The experimental results from a series of monotonic triaxial compression tests under both undrained and drained conditions clearly indicated that there exists a critical state line that defines the void ratios (e) and the associated effective mean normal stresses (p') at critical states, and the critical state line is plotted as a straight line in e-(p')^α plane, where α is a material constant. For the Tung Chung sand and the UST sand, α is 0.66 and 0.416, respectively. The critical state line is valid for both drained and undrained triaxial compression tests.

To predict the stress strain behavior under dilative hardening, a constitutive soil model based on the framework proposed by Li (1997) was employed. The model parameters of both the Tung Chung sand and the UST sand were calibrated. The model predictions and the experimental results match each other well, which verifies the principle of the modeling framework.