Stiffness design for granular materials - A theoretical and experimental approach

This study was prompted by a recent project investigating the seismic behaviour of a small scale model pile embedded in layered soils. The underlying problem in looking at the soil-pile interaction is in the representation of the material surrounding the pile and of its boundaries at infinity. The necessity to achieve a certain stiffness ratio between the soil layers in order to secure the similitude between the prototype soil and the model soil required a theoretical and experimental investigation into how the stiffness of a granular material could be designed and physically achieved. Rubber granules and sands were employed to model soil profiles in a shear stack. Considerations of stiffness of granular mixtures, as well as experiments of density/stiffness design are presented. Various dynamic testing techniques were employed to measure the stiffness of the layered deposits. A comparison is made between the measured and the theoretical values of stiffness.