Document: NUREG-0800
Document ID: 73dc4705-6dff-4f44-87ee-2a6f76cc6536
Document Type: srp
Title: OTHER SEISMIC CATEGORY I STRUCTURES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1319/ML13198A258.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.8.4
CFR Part: 
CFR Title: 

Content:
actions between structures. • Effects of groundwater on static and dynamic soil pressure. Field measurements and experimental investigations confirm the wide variation in soil pressures depending on the different factors identified above. Therefore, the enhancement to the SRP describes three methods to compute seismically induced lateral soil pressures on embedded walls, which should bound the uncertainties in the estimates for most design situations. The governing pressures of the three methods should be considered in the design. The governing pressures should also be determined based on the pressure distribution that generates the maximum member forces used for design of the foundation walls. The first two methods are based on linear or equivalent-linear elastic assumptions, while the third method is based on the passive pressure and accounts for inelastic strains, albeit in a simplified manner. A clarification is also made relative to the passive pressure; the intent is to ensure that all or part of the passive pressure is incorporated in the design regardless of whether the maximum passive state condition has been reached in the soil (as indicated above, the latter is rarely the case for embedded walls in NPP structures). The displacement-dependent fraction of the passive pressure that is effectively mobilized can be determined from nonlinear FEM computations or from experimental results. The enhancement also emphasizes the review of the analysis assumptions. This is important because soil pressures can vary substantially depending on the different factors identified above. Conservative assumptions are thus critical. The second method has been added to the SRP in light of recent NPP designs, in which seismic soil pressures have been computed using an embedded SSI/FEM analysis model. This is a general approach that is appropriate under the linear elastic or equivalent-linear elastic strain assumption and may address some of the issues discussed above. However,