A centrifuge test (ODA01) was used as a proof-of-concept test to investigate the effect of vertical differential settlement on crack formation in a model levee. The Yolo loam embankment levee and its foundation were 250 mm and 62.5 mm high in prototype scale, respectively. Viscous pore fluid was used to simulate water behind the levee at a height of 225 mm and the test was conducted at 40g. The foundation of the levee included a moving part (a hydraulic table) and a non-moving part (a jointed wood table). The hydraulic actuators were extended to a maximum height of 25 mm before the start of the test. In the centrifuge, the hydraulic table was lowered to a maximum settlement of 25 mm to simulate the differential settlement of the levee. Hairline, transverse and longitudinal cracks were effectively induced in the levee through this vertical differential settlement. Furthermore, seepage flow was initiated through the cracks. The seepage flow stopped after some time without significant erosion, likely due to swelling of the soil around the crack and lowering of the upstream water level.

The Center for Geotechnical Modeling (CGM) at UC Davis provides users access to world-class geotechnical modeling facilities, including 9-m and 1-m radius centrifuges with shaking tables, to enable major advances in the ability to predict and improve the performance of soil and soil-structure systems affected by earthquake, wave, wind and storm surge loadings.

This poster describes the NHERI Experimental Facility with Geotechnical Centrifuges at the University of California at Davis. The vision, uniqueness, and history of the facility are described.

Numerous industries are concerned by the humanitarian, environmental, and economic consequencesof debris flows, landslides and material run-outs. However, the run-out behavior following a loss ofconfinement e.g., dam failure, is not well understood. The material’s complex constitutive behaviormeans multiple mechanisms contribute to the deformation e.g., slope instability, seepage forces, erosionor static liquefaction. In this study, centrifuge models of fly ash deposits, with varying initial depositdensity and water table height, were subjected to a rapid loss of lateral confinement. Deformation,pore pressure and water content measurements were used to investigate and separate the mechanismsgoverning the run-out. Static liquefaction was observed in deposits initially looser than the critical stateand led to a rapid material outflow. Slope instability was the initial failure mechanism for denser depositsor those with reduced water tables, with transient stability due to dilation-induced negative excess porepressures followed by progressive failures caused by seepage pressures from drainage and pore pressuredissipation. Cone penetration tests, performed before loss of confinement and with different penetrationrates, characterized the material run-out and volume change tendencies and may be a practical tool forassessing the run-out risk of deposits in the field.

A centrifuge model test was used to examine the effect of soil interlayering on the measured cone penetration resistance in a layered soil model. The centrifuge model included a layer of loose or dense sand with varying thickness between overlying and underlying layers of low plasticity clayey silt. The sand was loose with a relative density of 44% on one side of the model, and dense with a relative density of 88% on the other side. The clayey silt had a plasticity index (PI) of 6 and over-consolidation ratio (OCR) of about 1.5. Multiple cone penetration soundings were performed using cone penetrometers with diameters of 4, 6 and 10 mm. The results showed the measured tip resistance in layered soil as well as the sensing and development distances depend on cone diameter, sand layer thickness, and stiffness contrast between the subsequent soil layers. The results provide insights on the effect of thin layer presence on cone tip measurements and an archived dataset for evaluating design procedures and numerical analysis methods. The data has been subject to quality control before publishing. The process by which it was assessed and the issues found are described in the Data Report.

A set of 1-m radius centrifuge tests on saturated loose Ottawa sand models treated to various cementation levels and subjected to multiple shaking events. Changes in cone penetration resistance and shear wave velocity are monitored throughout each test.

A lightly cemented model was saturated with a de-aired viscous fluid. The model was subjected to a series of shaking events at 80-g. Shear wave velocity and cone penetration measurements were obtained at select times.

A set of 1-m radius centrifuge tests on saturated loose Ottawa sand models treated to various cementation levels and subjected to multiple shaking events. Changes in cone penetration resistance and shear wave velocity are monitored throughout each test.

A set of 1-m radius centrifuge tests on saturated loose Ottawa sand models treated to various cementation levels and subjected to multiple shaking events. Changes in cone penetration resistance and shear wave velocity are monitored throughout each test.

A lightly cemented model was saturated with a de-aired de-ionized water. The model was subjected to a series of shaking events at 80-g. Shear wave velocity and cone penetration measurements were obtained at select times.