Strain-Dependent Creep Behavior of Athabasca Oil Sand in Triaxial Compression

AbstractOil sand is a dense granular material with interlocking fabric. As a strain-softening material, oil sand exhibits a more complex creep behavior than that of strain-hardening geomaterials. The creep behavior of oil sand could be excessive and detrimental to surface and subsurface facilities in the long term. This paper describes a study on creep behavior of oil sands. A series of triaxial compression creep tests were performed on oil sand to investigate its creep behavior at different stress and strain levels. The creep behavior of oil sand is dependent not only on both time and stress but also on initial inelastic strain, and it is influenced by the growth of shear bands. A strain-dependent creep model was proposed to describe the prepeak creep behavior of the oil sand. With this model, the dependence of creep rate of oil sands on time, stress, and strain is taken into consideration properly. It was argued that the change in the microstructure of oil sand could be uniquely represented by the inelastic strain of oil sand. Therefore, the potential for plastic flow could be used in modeling oil sand creep. Finally, the general creep rate–stress–inelastic strain relations of strain-hardening and strain-softening soils were developed according to the critical state theory of soil and the inelastic strain-dependent creep rate of soils.