ERI: Laboratory Investigation into Effects of Vertical Ground Motion on Liquefaction Resistance and Consequences

California State L A University Auxiliary Services Inc., Los Angeles CA

Investigators

Abstract

This Engineering Research Initiation (ERI) project investigates how simultaneous vertical and horizontal shaking, induced by ground motions during earthquakes, influences the behavior of sandy soils, particularly the triggering of liquefaction and the resulting ground settlement. While most earthquake design methods consider only horizontal shaking, newer data from recent earthquakes show that vertical accelerations can be just as strong, and may significantly affect infrastructure safety. This research uses specialized laboratory equipment to simulate real earthquake shaking and will generate new insights that improve how engineers evaluate and design for soil liquefaction. Results from this project aim to improve the seismic resilience of infrastructure in earthquake-prone regions. Graduate and undergraduate students will receive hands-on training in testing, data analysis, and earthquake engineering designs. The project will also produce open-access datasets to support other researchers in the calibration of numerical models. This project employs confined cyclic simple shear testing to investigate the effects of vertical ground motions on liquefaction triggering and post-liquefaction reconsolidation. A series of element-level laboratory tests will impose irregular and broadband transient loading histories along both vertical and horizontal axes, including harmonic, modulated, phase-shifted, and realistic ground motions. Testing will be conducted on Ottawa sand specimens prepared at consistent density and saturation, using multi-stage shear-drain-reconsolidate testing procedures. Ground motions will be selected from the Pacific Earthquake Engineering Research Center Ground Motion Database. The research will produce a comprehensive dataset to support validation of constitutive models and will evaluate various intensity measures (e.g., CAV, Ia, VSI) for their ability to predict post-liquefaction volumetric strain (re-consolidation). Results will be made available through NSF’s DesignSafe repository. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.