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:
ergranular stress due to the weight of the soil above the depth of interest and Ko is called the at-rest coefficient of earth pressure. The parameter Ko is typically estimated to be approximately 0.5. Under seismic conditions, the pressures change from the static case and are primarily controlled by the relative motion developed between the wall or structure and the free- field. If the wall or structure moves away from the soil, these dynamically induced pressures decrease from the static at-rest pressures. This stress state is termed the active state. The minimum value of this active state is estimated for ordinary conditions as Ka x σv, where Ka is called the Rankine active coefficient of earth pressure. The value of Ka is less than Ko and is approximately 0.33. If the wall or structure moves into the surrounding soil, the pressures increase above the static at-rest condition. This increased stress state is termed the passive state. The maximum value of this passive state is estimated for ordinary conditions as Kp x σv, where Kp is called the Rankine passive coefficient of earth pressure. For ordinary granular soils, the value of Kp is approximately 3.0 or more. For typical granular materials, it is expected that the total pressures acting on the wall under seismic conditions will change from the static at-rest case to no less than the Rankine active pressure and to no more than the Rankine passive pressure. Therefore, for ordinary granular materials, the total horizontal pressure coefficients (static plus 3.8.4-39 Revision 4 – September 2013 dynamic) can be expected to vary during the seismic motions from about 0.5 to no less than 0.33 and to no more than 3.0. For more general soil materials that possess both cohesive and frictional shear strength, the formulation of the maximum and minimum Rankine states is more complex to delineate. Nevertheless, under seismic conditions, the total horizontal pressures are also bounded by the maximum and minimum Rankine