Document: NUREG-0800
Document ID: 73747cf4-ff95-449b-b6b0-53dc0755b9e0
Document Type: srp
Title: OTHER SEISMIC CATEGORY I STRUCTURES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12353A382.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.8.4
CFR Part: 
CFR Title: 

Content:
rains. It is clear that the true stress/strain state in the soil under seismic conditions is likely to deviate from the inelastic limit states discussed above. Important additional factors to consider are: • Kinematics of the problem. Significant differences in the pressure distribution profile and the stress/strain state in the soil could occur depending on whether the embedded walls are assumed rigid or flexible, whether the base of the walls are allowed to rotate or slide relative to the soil, whether the structure is supported on stiff or flexible soil, and whether the overall motion of the structure includes a significant rocking component or not. 3.8.4-40 Draft Revision 4 – December 2012 • Heterogeneity of the soil mass. An additional complication occurs if there is significant difference in stiffness between different backfill and in situ soil layers, and especially if the structure is partially embedded in rock. In the latter case, a large stress discontinuity is expected in the interface region between soil and rock. • In typical NPP configurations, linear or equivalent-linear strains would tend to produce conservative estimates of pressures; however, there may be specific configurations for which the opposite occurs. • Separation of the soil from the wall. • Structure-soil-structure interactions 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 proposed 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