Pile Foundations (2006-2014)
NEESR-SG: Experimental and Micromechanical Computational Study of Pile Foundations Subjected to Liquefaction-Induced Lateral Spreading
Principal Investigator: Ricardo Dobry
This research objective is to understand the phenomenon of sand liquefaction during lateral spreading near pile foundations; solve the engineering questions on how to design pile foundations against lateral spreading both in simplified terms as well as in terms of providing a basic understanding for appropriate analytical platforms; and clarify the correct way to use centrifuge modeling in future research and engineering applications.
This is done through a research plan using the U. at Buffalo 1 g 2D shaking, 6 m-tall laminar box container NEES facility, the RPI NEES centrifuge facility, and the large E-Defense Miki City, Japan shaking table; use of novel advanced sensors to measure soil accelerations, deformations and pressures during shaking; and micromechanical Discrete Element (DEM) numerical experiments and finite element (FE) analyses at RPI, UC San Diego and Tulane University; all integrated by an appropriate identification and analysis framework including system identification and visualization capabilities.
Centrifuge Testing Program
A series of Centrifuge tests is currently performed in the Centrifuge facility at RPI to assess the liquefaction susceptibility of a 6m deposit of Ottawa Sand. The 1D laminar box and shaker are used in this regard where the seismic response of a 24cm fully saturated Ottawa Sand deposit is tested at 25g and subjected to 50 cycles of an equivalent uniform harmonic shaking having different amplitudes. The spatial and temporal distribution of the accelerations, pore-pressure ratios, lateral spreading and compressibility are recorded with depth throughout the model using accelerometers, pore-pressure transducers and LVDTs. Surface trackers are installed on the surface of the model and tracked using the high-speed camera in order to asses the pattern and velocity of the lateral spreading at the ground surface. The parametric study involves testing the same setup for different relative densities and Over-Consolidation Ratios of the soil before shaking. The attached figures show the layout of one of the models, its instrumentation and wiring, and the DAQ of the Centrifuge with the sensors hooked just before running the experiment.