Centrifuge test RLH01 on prefabricated vertical drains for liquefaction remediation

This is the third test in a series of three dynamic centrifuge tests designed to evaluate the effectiveness of prefabricated vertical drains in mitigating liquefaction. Centrifuge testing was performed using the 9-m radius centrifuge at the NEES@UCDavis Center for Geotechnical Modeling. The centrifuge model consisted of sloping ground with liquefiable sand overlain by a low-permeability crust. Water was used as the pore fluid. A centrifugal acceleration of 15g was applied.

There were three treatment areas within the model - one untreated, one untreated but containing non-draining tubes, and one drain-treated. Each treatment area consisted of three distinct soil layers: (1) a 0.75 m (prototype scale) thick layer of dense Nevada sand (DR ~ 85%) overlain by (2) a 5 m (prototype scale) thick layer of loose, liquefiable Nevada sand (DR ~ 40%), which was in turn overlain by (3) a 1.5 m (prototype scale) thick layer of Yolo Loam clay. Accelerometers and pore pressure transducers and linear potentiometers were placed within the model to measure its response.

Two earthquake acceleration-time histories were used as the principal input motions: PAC175, a short duration motion from the 1994 Northridge earthquake with only a few significant cycles (D5-75 = 0.62 s, number of equivalent uniform cycles at 65% of the peak (Neq) = 2 to 4), and PSL180, a longer duration motion from the 1971 San Fernando earthquake with more cycles (D5-75 = 5.68 s, Neq = 11 to 15). Shaking took place orthogonal to the slope, and a total of 9 shaking events were applied to the model. Scaled PAC175 and PSL180 input motions, ranging in PGA from 0.11 to 0.95 g, were used for the first 8 shaking events, and a sine wave with 20 cycles of motion at a frequency of 2 Hz and a PGA of 0.6 g was used for the final shaking event.

***Detailed information regarding instrument locations, sensor calibrations and gains, channel names, shaking sequences, file naming convention, etc can be found in RLH01_metadata.xls in the Documentation directory.***