RAPID: Evaluation of Pre and Post Blast Liquefaction Soil and Site Parameters

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Soil liquefaction is a phenomenon that can occur in saturated, loose sand and silt sediments during earthquake shaking which causes these soils to behave as a viscous fluid. This results in loss of strength and stiffness, often causing significant damage to civil infrastructure, such as buildings, bridges, and dams. Advances in soil liquefaction engineering have aided engineers in prediction of the initiation of liquefaction (triggering) and its consequences, thereby reducing casualties and damage to infrastructure. However, changes in soil properties both during and following liquefaction, and the affect that these changes can have on soil stiffness and settlement require further study to improve prediction of both post-liquefaction response and behavior during future earthquake events. This Grant for Rapid Response Research (RAPID) project will leverage existing field-testing equipment available from the Natural Hazards Engineering Research Infrastructure (NHERI) RAPID facility and blast testing already occurring as part of another NSF award to measure changes in soil parameters as a result of liquefaction. Measurements will be taken before, during, and after blast-induced liquefaction tests that are scheduled in New Zealand. The blast-liquefaction testing will occur at two locations: one with natural soils and one with soils that have been improved by resin injection. The site offers the opportunity to evaluate both native soils that liquefied during the 2010-2011 Canterbury Earthquake Sequence, as well as improved soils that represent a promising ground improvement technique to mitigate differential settlements and surface manifestations of liquefaction. The results have immediate application to regions of the United States which are prone to liquefaction. This project will enhance international collaboration among scientists and will involve students in an international research experience.The objective of this RAPID project is to further understand liquefaction effects on soil (e.g., shear wave velocity [VS], settlement) and site (e.g., fundamental frequency, amplification, vulnerability index) parameters by utilizing equipment from the RAPID facility to measure properties during blast-induced liquefaction testing occurring in New Zealand. Equipment that will be utilized from the NHERI RAPID facility includes: Seismometers, an instrumented dynamic cone penetrometer (DCP), multi-channel analysis of surface waves (MASW), and a 3D terrestrial laser scanner. The outcomes of this research will result in measurements of: (1) fundamental frequency and amplification factors before, immediately following liquefaction as the pore pressures dissipate, and after liquefaction when pore pressures have fully dissipated, (2) VS and DCP resistance before, immediately following, and after liquefaction, and (3) spatial ground deformations (i.e., settlement and lateral movement) at the liquefaction site using lidar scanners. A unique dataset of soil and site parameters will be created for pre and post liquefaction scenarios at two varying sites, enabling evaluation of changes in soil and site parameters as a result of liquefaction and improving our understanding of the effect of these changes on design of earthquake resilient infrastructure.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.