Strain-Dependent and Stress-Dependent Creep Model for a Till Subject to Triaxial Compression

Soil exhibits creep behavior, in which the deformation of soil develops with time at a state of constant effective stress. A series of triaxial compression creep tests was performed on a saturated till to investigate the creep behavior at different effective stresses and strains of the samples. In the tests, the saturated till was allowed to creep in single, multiple, and stepwise stages. The dependency of creep rate of the saturated till on time was examined using the test data. It was found that the time-dependent creep rate models are incapable of describing the creep behavior of soil under the condition of multiple-stage creep, i.e., complex load conditions. A strain-dependent and stress-dependent creep model of the saturated till subject to triaxial compression was proposed. In the model, the creep rate of soil was formulated as a function of inelastic strain and effective stresses instead of time and effective stresses. This model could describe the dependencies of soil creep rate on time, strain, and effective stress observed in the triaxial compression creep tests. Test data obtained in the creep tests were used to verify the proposed model. Moreover, a methodology to accelerate the creep test for soil was developed