Development of validated methods for soil-structure interaction analysis of buried structures: Project

The seismic response of underground structures is a complex soil-structure interaction (SSI) problem in which two fundamental mechanisms are at play. Kinematic SSI is concerned with the motion of the structure in the presence of spatially variable ground motions and the interface pressures that develop as a result of different structural and free-field motions. Inertial SSI captures the soil reactions that develop to resist inertial forces associated with the acceleration of the structure. The kinematic component is generally considered to be most significant for embedded structures, due to their modest mass. Existing methods of analysis for the seismic response of embedded structures are not based on a rational conceptual framework that recognizes the essential role of SSI in the response prediction. These methods of analysis therefore have an unknown degree of reliability for the problem. We propose a two-year project that will significantly advance our understanding of SSI for embedded structures. The major elements of the proposed work are as follows: 1) Utilizing the Center for Geotechnical Modeling (CGM) 1 centrifuge modeling facility, perform an experiment consisting of two representative structures embedded in backfill per Caltrans Standard Plans A62E and A62F. 2) Compare the experimental findings with the recently proposed method in National Cooperative Highway Research Program (NCHRP) 611 report and establish the validity (or lack thereof) of this method for the specific Caltrans configurations tested. 3) Formulate preliminary recommendations for Caltrans practice and identify future research needs in this area, as needed.