Nonlinear 3-D modeling of dense sand and the simulation of a soil-structure system under multi-directional loading

The seismic performance of nuclear power plants (NPPs) constructed on compacted, dense sands depends on their cyclic response. NPPs founded on a thick deposit may experience nontrivial settlements due to small, but accumulated volumetric strains during an earthquake. Nonlinear, three-dimensional (3-D) numerical simulations can be utilized to assess the deformations of the soil-structure system. This work examines the performance of a class of distributed element constitutive models which has a parallel-series Iwan type distribution of elastic - perfectly plastic nested components. The performance evaluation is limited to deviatoric space since the volumetric component is yet not implemented. Soil-structure 3-D interaction and single element numerical simulations are compared to dynamic centrifuge and cyclic direct simple shear (cDSS) tests respectively. The simulations reasonably capture the measured shear behavior in small to medium shear strain ranges achieved in the centrifuge. However, the constitutive model deviates from measured response at the large shear strain levels achieved in cDSS.