Variable Bulk Modulus Constitutive Model for Sand

A quasi-linear elastic constitutive model is proposed to describe the behavior of sand well below failure. It is based on isotropic compression tests and captures the increase in stiffness due to confinement—a unique property that makes sand stiffer under certain applied loads. The model traces the increase in stiffness by describing the instantaneous bulk modulus in terms of the effective mean stress and two constitutive parameters: the initial bulk modulus and the ultimate volumetric strain. The validity of the model is examined by checking how closely the proposed mathematical formulation represents high quality isotropic compression tests reported in the literature.