UCLA Civil and Environmental Engineering

A fragility model for seismic deformations of levees was developed in a separate study using case history data from the Shinano River region of Japan (SRJ). In that model, levee fragility was shown to be principally related to ground motion intensity, geomorphology, and ground water level relative to the levee base. Our objective in this manuscript is to demonstrate the applicability of the developed fragility models for geotechnical conditions along urban levees in the Central Valley region of California (CVC). For this purpose, we compare SPT penetration resistance data (in the form of energy- and overburden-corrected blow counts) between regions for common soil types conditional on geology and topography. Among the geologic categories considered, arguably the most important is Holocene flood plain deposits, which comprise 38% of investigated sites in CVC and 97% in the SRJ. Within this geological unit, we find penetration resistance data for coarse-grained soils in the SRJ and CVC study regions to be similar, whereas for fine-grained soils the CVC sediments are stiffer. For two other geological units (Holocene basin and Pleistocene), both coarse- and fine-grained deposits in the CVC are stiffer than Holocene floodplain deposits. We also considered topographical conditions (elevation, ground slope and river gradient) as alternative means for sorting the data, with the general conclusion that such indicators are less capable than geology of describing variations of penetration resistance within the respective regions. The results provide insight into the relative vulnerability of levees in the two regions for given levels of ground motion amplitude.