Centrifuge Modeling of the Effect of Preshaking on the Liquefaction Resistance of Silty Sand Deposits

Abstract

Field observations suggest that preshaken natural sands in some seismic regions have high liquefaction resistance as a result of geologic aging and/or preshaking. This paper focuses on the young silty sand deposits located in the Imperial Valley of California. Recent deposition and intense seismic activity in the Valley suggest that preshaking is the main cause of their increased liquefaction resistance. The first part of the paper examines the liquefiable layer at the Wildlife site, which may have been deposited by flooding approximately between 1905–1907. The site was instrumented with accelerometers and piezometers in 2005, providing data over the last 10 years. The following conclusions are reached from this and from the catalog information on earthquakes before 2005: (1) Since 1907, the Wildlife layer has been subjected to approximately 60–70 earthquakes having