Instrumented field sites provide essential information for understanding and modeling ground response generated by earthquake shaking of liquefiable sites. For example, several instrumented liquefaction sites have been strongly shaken by earthquakes since 1987, including the Wildlife Liquefaction Array (WLA) in southern California and the Port Island Downhole Array (PIDA) site near Kobe, Japan, highlighted in this paper. Measured ground responses at the WLA and PIDA sites are compared with predicted ground responses that should have occurred in the absence of soil softening and liquefaction. At these strongly shaken sites, soil softening during the liquefaction process reduced short period ( < 0.7 sec) while increasing long period ( > 1.0 sec) spectral accelerations. Two new liquefaction sites are being instrumented as part of the NSF NEES program: (1) the WLA site has been reestablished with more FBA's and piezometers and more ground deformation monitoring capability; (2) a previously instrumented site, the Garner Valley Downhole Array (GVDA), is being enhanced with an additional downhole FBA, new piezometers, and a soil-foundation-structure-interaction experiment (not discussed herein). Data from these sites will be streamed to the NEES-grid in near real time.
展开▼
