| This thesis describes an assemblage of facilities, equipment and experimental techniques which have been developed at Rensselaer Polytechnic Institute (RPI) to aid in small-scale physical modeling of geotechnical systems. The goal of this work has been to achieve an experimental capability for studying earthquake phenomena in geotechnical systems under controlled laboratory conditions. Toward this end, as part of this thesis a geotechnical centrifuge facility has been developed and configured for measuring the dynamic behavior of small-scale models of soil- and soil-structure systems. A 100 g-ton centrifuge, built to RPI specifications, has been installed in a newly constructed underground enclosure that augmented RPI's existing geotechnical laboratory. Two servo-hydraulic shakers for applying base input motion to containers of soil have been designed and fabricated as part of this thesis. These shakers have been optimized to provide the high-force, high-frequency shaking required to adequately model seismic loading in the elevated-g environment on the centrifuge. The bearing system which supports the shaken load has been carefully designed to constrain the shaking motion to one horizontal direction, minimizing uncontrollable transverse components. Finally, a flexible-walled, stacked ring model container has been designed, constructed and tested. This laminar box is designed to provide suitable boundary conditions for modeling a column of soil in the free-field subjected to horizontal input motion applied at the base. In addition, the container has been specially designed to permit large localized lateral strains, making it useful for studies in lateral spreading and flow failures due to liquefaction.; This equipment has been designed to operate with a specific model of centrifuge, the Acutronic 665. However, it can be utilized with any centrifuge having sufficient payload capacity. In addition, the equipment is scaleable, and similar dynamic capabilities can be developed for geotechnical centrifuges of virtually any size. |
