When a nuclear power plant (NPP) structure is subjected to beyond-design-basis seismic motions, a localized nonlinear effect on the soil-structure system is attributed to separations between the structure and the surrounding soils such as basemat uplift. Experiments involving field tests for real seismic events are usually difficult because of the low probability for large earthquakes at any particular site. To this end, the magnitudes of blast-induced ground motions at a coal mine have been found to be predicatable and can reach very large values. An approach has been developed to investigate whether the strong ground motions recorded at this coal mine can be used to evaluate the basemat uplift effect. This approach involves the use of a scaled ground motion to establish the relationship between the basemat uplift and the peak ground acceleration (PGA). This paper summarizes the field measurements for the ground motions at a coal mine by the Japan Nuclear Safety Organization (JNES) and a method using large scale finite element analyses for basemat uplift assessment performed by Brookhaven National Laboratory for the US Nuclear Regulatory Commission.

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