Reduced-Order Sand Model for Ground Response Analysis

Abstract

“Ground response” in geotechnical earthquake engineering refers to the response of level ground subjected to seismic loading originating from the underlying rock formation. Catering to this special loading condition, the stresses and strains in soil can be sufficiently represented by four-component vectors instead of second-order tensors. Correspondingly, the order of a “full-fledged” soil model can be reduced, resulting in a great improvement in the efficiency and robustness of computation. This paper presents a simplified and reduced-order version of a bounding surface hypoplasticity model that captures the essential behavior of granular soils under the ground response loading conditions. To make the model well behaved under nearly-zero mean normal stress conditions, a curved phase transformation surface is proposed. An attempt has been made to minimize the number of model parameters, and most of the parameters are associated with commonly used engineering properties. The model has been integrated into a fully-coupled effective stress procedure and has shown its effectiveness and robustness in analysis.