Pile-supported Wharves Subjected to Combined Inertial and Lateral Ground Deformation Loads in Earthquakes

This award will improve the resilience of maritime transportation systems in earthquakes, including ports, terminals, and Navy facilities which are key components of economic prosperity, emergency response, and national security. In addition, ports are often designated centers for post-earthquake staging and relief efforts. However, seismic evaluation studies of port structures often encounter a knowledge gap related to soil-foundation-structure interaction in soils that are susceptible to liquefaction – a phenomenon that causes severe softening of soils in earthquakes.

The knowledge gap becomes even wider for foundations that are supported in silty soils (commonly encountered at port facilities) as there is no consensus in the geotechnical community on how to predict the behavior of silty soils in earthquakes. This research will address these knowledge gaps by performing a series of advanced physical experiments and numerical simulations.

The findings of this research will result in safer, more resilient maritime transportation systems. Close collaborations with industry partners will ensure that the knowledge produced in this study will benefit the broader engineering community. Characterizing the behavior of silty soils in earthquakes will have a significant effect in assessing, and reducing, the risks associated with an imminent Magnitude 9 Cascadia Subduction Zone earthquake in the Pacific Northwest of the U.S. with substantial economical and societal impacts.

The research will also be complemented by a partnership with the LSAMP program at Portland State University to help enhance STEM education with emphasis on diversity.

This research has two specific objectives: (1) to investigate a collapse mechanism due to incremental yielding in in-ground pile plastic hinges when subjected to many cycles of loading in long-duration earthquakes, and (2) to quantify the interaction of inertial and kinematic loads on piles with respect to various ground motion characteristics, pile properties, soil profiles, and soil properties. These objectives will be achieved by performing a series of large-scale geotechnical centrifuge tests at the Natural Hazards Engineering Research Infrastructure (NHERI) facility at UC Davis combined with numerical parametric simulations.

The results of this research will provide an in-depth understanding of the interaction of inertial and kinematic loads on piles in liquefiable soils which are needed for seismic evaluation studies of new and existing ports as well as other pile-supported structures including highway bridges, buildings and nearshore structures.

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.