ERI: laboratory investigation into effects of vertical ground motion on liquefaction resistance and consequences

The National Science Foundation's Division of Civil, Mechanical, and Manufacturing Innovation (CFDA 47.041 – Engineering) awarded $200,000 to California State University, Los Angeles (CAL State LA University Auxiliary Services Inc.) under the Engineering Research Initiation (ERI) program for a two-year project (January 1, 2026 – December 31, 2027). This award supports laboratory research investigating the effects of vertical ground motion on soil liquefaction resistance and post-liquefaction ground settlement. The primary deliverable is a comprehensive experimental dataset generated through confined cyclic simple shear testing of Ottawa sand specimens subjected to simultaneous vertical and horizontal earthquake-induced loading. Testing will employ multi-stage testing procedures with ground motions selected from the Pacific Earthquake Engineering Research Center (PEER) database, including harmonic, modulated, phase-shifted, and realistic transient loading histories. The research will evaluate various intensity measures (e.g., CAV, IA, VSI) to improve understanding of how vertical accelerations influence liquefaction triggering and infrastructure performance.

In addition to the experimental dataset, the project will produce open-access research data to support validation of constitutive models and enable calibration of numerical models by the broader research community. Educational deliverables include hands-on training and mentorship for graduate and undergraduate students in earthquake engineering testing, data analysis, and seismic design methodologies. The research outcomes will directly inform improved seismic design practices and evaluation methods for infrastructure in earthquake-prone regions, ultimately enhancing the seismic resilience of built systems.

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.- subawards are not planned for this award.