Seismic response of sand beds in a laminated shear stack: physical and numerical modelling

This paper presents the design and workings of a new type of laminated shear stack container. Several experiments were conducted involving a sand bed placed inside the shear stack that was excited horizontally under a variety of input excitations. A two-dimensional (2D) finite element model of the shaking table and laminated shear stack containing the sand bed was developed, incorporating details of the table and laminated shear stack design. The capability of the finite element model to replicate the dynamic response of the naked table, and of the sand bed inside the laminated shear stack when interacting with the table, were verified. The finite element model was extended to explore important aspects of the sand and laminated shear stack behaviours, including how the use of energy absorbing boundaries in the laminated shear stack enable parts of the sand model to exhibit field-equivalent responses. For low to moderate ground shaking it is shown that the chosen stiffness for the energy absorbing boundaries does not have a significant influence on the seismic performance of the sand bed at its center. Demonstrations of similitude are also given. Large size differences between model and field scales may be associated with attenuations of stress waves and de amplifications of accelerations that are not insignificant.