Seismic Performance of Underground Reservoir Structures: Insight from Centrifuge Modeling on the Influence of Structure Stiffness

Abstract

The available simplified analytical methods for the seismic design of underground structures either assume yielding or rigid-unyielding conditions. Underground reservoir structures do not fall into either of these categories. In this paper, we present the results of three centrifuge experiments that investigate the seismic response of stiff-unyielding buried structures in medium dense, dry sand and the influence of structure stiffness and earthquake motion properties on their performance. The structure to far-field spectral ratios were observed to amplify with increased structural flexibility and decreased soil-confining pressure at the predominant frequency of the base motion. Lateral earth pressures and racking displacements for a range of structural stiffnesses were compared with procedures commonly used in design. Pre-earthquake measured lateral earth pressures compared well with expected at-rest pressures. However, none of the commonly used procedures adequately captured the structural loading and deformations across the range of stiffness and ground motions for which these reservoirs must be designed. Further, it is unclear whether the current methods of analysis provide results that are conservative or not conservative for engineering design purposes. This identifies a critical need for improved methodologies to analyze and design underground reservoir structures.