The CGM’s scientific vision is that our 9-m and 1-m radius geotechnical centrifuges together provide the unique and versatile modeling capabilities required for realizing major scientific and engineering advances in our discipline’s ability to predict and improve the performance of soil and soil-structure systems affected by earthquake, wave, wind and storm surge loadings. Centrifuges enable the use of scale models to accurately represent nonlinear, stress-dependent responses of soil masses that are many times larger than is possible on the world’s largest 1-g shaking tables. Our centrifuge facilities enable the building of basic science knowledge; the validation of advanced computational models from the component to holistic system level; the validation of innovative mitigation strategies; and the integration of research, education, and outreach activities in the training of a broad and inclusive STEM workforce.
The 9-m radius centrifuge, with its many advanced technologies, has the largest radius of any centrifuge with a shake table worldwide. The 9-m centrifuge provides the unique ability to: (1) construct soil and soil-structure models with holistic system levels of complexity and (2) obtain measurements of complex local mechanisms through inverse analyses of data from dense instrumentation arrays, neither of which are possible on the smaller centrifuges typical throughout the world. The combined power of these capabilities has enabled major scientific and engineering advances for a number of soil and soil-structure systems in the past decade.
Fig. Models of pile pinning in opposing bridge abutments
For example, models with holistic system levels of complexity have produced advances through the first-ever measurements of non-linear dynamic multi-story structure-soil-structure interactions; first-ever measurements of nonlinear dynamic interactions between bridge approach embankments and piled abutments (image above; Armstrong et al. 2013); one-of-a-kind measurements of the uplift mechanisms for a submerged tunnel surrounded by liquefiable sand backfill (i.e., BART transbay tube shown below; Chou et al. 2011 and Fugro); and first-ever system-level dynamic measurements of soil profiles remediated/treated with geosynthetic drains, soil-cement blocks, and soil-cement grids.
Fig. Models of submerged BART tube
Similarly, examples of major advances enabled by inverse analyses of data from dense instrumentation arrays in the 9-m centrifuge include the first-ever measurements of dynamic soil-pile load-transfer (p-y) mechanisms in liquefying soil, first-ever measurements of dynamic soil-pile-cap load transfer mechanisms in laterally spreading ground, first-ever measurements of foundation rocking effects on nonlinear demands in shear-wall gravity frame systems, and first-ever measurements of pore pressure diffusion and volumetric strain profiles leading to strain localizations (or water film formation) between liquefying sands and overlying clay layers.
The 1-m radius centrifuge complements the 9-m centrifuge by enabling high throughput of relatively simple (component-level) tests for exploring new ideas and rapid parametric studies. In addition, the 1-m centrifuge provides an effective and economical training ground for users to gain hands-on experience in centrifuge modeling.
The CGM seeks to improve the science of our users at the proposal, design, construction, testing, and interpretation stages through personalized guidance and technical support. We enable our users to integrate their research, education, and outreach activities to contribute to a globally engaged and diverse STEM work force, leverage partnerships between industry and academia, and improve the well-being of U.S. citizens through safer and improved management of infrastructure.