Large-Scale Liquefaction and Postliquefaction Shake Table Testing

Abstract

A large-scale liquefaction testing program was carried out on a 10-t shake table to better unite lab and field measurements before, during, and after seismic soil liquefaction. The objectives of this research include cone penetration test (CPT) and shear-wave velocity Vs measurements before and after liquefaction, observation of void ratio redistribution due to liquefaction, measurements of residual strength during liquefaction, measurements of postliquefaction volumetric and shear strains, and measurements of ejecta due to liquefaction. A large cylindrical simple shear container was developed that is roughly 1.5 m tall by 2.3 m diameter to test a 6.4-m3 sample of water-pluviated Monterey sand in a series of tests. The sample was excited using a sine wave at its resonant frequency to trigger and maintain liquefaction over 15 s of loading. Vertical arrays containing accelerometers and pore pressure transducers were arranged throughout the sample. Cone penetration and shear-wave velocity tests were performed before and after liquefaction. During liquefaction, T-bar measurements along with acceleration and pore pressure measurements were acquired. Void ratio redistribution was observed as inferred from changes in the measured preliquefaction and postliquefaction CPT tip resistance with depth. Volumetric strains and shear strains were observed and measured using displacement transducers. Ejecta volume that was expelled from the top of the container was observed and quantified. The liquefied residual strength was measured using the T-bar test. A summary of the results and how these relate to the broader field of liquefaction engineering are presented.