RAPID/Collaborative Research: Liquefaction Mitigation of Silts using MIDP and Field Testing with NHERI UTexas Large Mobile Shakers

University Of Texas At Austin, Austin TX

Investigators

Abstract

The overall objective of this Grant for Rapid Response Research (RAPID) project is to evaluate the potential for a soil liquefaction mitigation technique in relatively fine-grained soils. This technique uses new advancements in the field of bio-remediation and will be tested in the field at a site located in Portland, Oregon. The project addresses a major seismic problem in Oregon, where many infrastructure facilities are founded on non-plastic to low-plasticity silts that are susceptible to liquefaction in a Magnitude 9 Cascadia Subduction Zone earthquake. The site selected for study are near the Critical Energy Infrastructure (CEI) hub located in northwest Portland, where 90 percent of the Oregon's liquid fuel and all jet fuels for Portland's airport are handled. The seismic vulnerability of fuel tanks at the CEI hub is a critical impediment to Oregon's resilience and energy reliability in the wake of a major earthquake. If the mitigation method in this project is proved to be effective in the field, it will provide a vertical step for adopting this solution for infrastructure founded on liquefiable silty soils. This will enhance the resiliency of Oregon after a major earthquake, and it can be adopted in other places with similar subsurface conditions. This project will evaluate the potential for microbially induced desaturation via dissimilatory reduction of nitrogen (denitrification) to mitigate liquefaction potential in relatively fine-grained soils. We hypothesize that 1) denitrification via two weeks of treatment can lower the degree of saturation to 80 percent in silty soils in the field, 2) this level of desaturation will eliminate pore water pressure generation in treated soils subjected to in-situ cyclic strains, and 3) the desaturation will persist for years due to the small pore size in silty soils (although this will need to be verified in subsequent research). Our approach to evaluate these hypotheses involves in-situ shaking using NHERI@UTexas field equipment at a site before and after treatment, and periodic monitoring of compression (P-) wave velocities during the next 3 to 5 years. 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.