Document: NRC Regulatory Guide
Document ID: a094549d-8685-4dad-b90f-c28c7d279a53
Document Type: regulatory_guide
Title: Geologic and Geotechnical Site Characterization Investigations for Nuclear Power Plants + HISTORY – HISTORY 08/2021 – DG-1392 , Proposed Revision 3 07/2014 – Periodic Review of Revision 2 – Reviewed with no issues identified 02/2001 – DG-1101 , Proposed Revision 2 (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2119/ML21194A176.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.132
CFR Part: 
CFR Title: 

Content:
increasing and may cause future slope instability in valley sites. Compare normal ground water levels with piezometric levels if data are available. Is a possible cause from past reduction in vertical stresses (e.g., deep glacial valley or canal excavations such as the Panama Canal in clay shales where pore water pressures were reduced by stress relief)? In situ shear strength from natural slopes Provides early indication of stability of excavated slopes or abutment, and natural slopes around reservoir area. Locate potential slide areas. Existing slope failures should be analyzed to determine minimum in situ shear strengths. Estimate slope angles and heights, especially at river bends where undercutting erosion occurs. Determine if flat slopes are associated with mature slide or slump topography or with erosion features. Are existing slopes consistently flat, indicating residual strengths have been developed? Swelling soils and shales Highly preconsolidated clays and clay shales may swell greatly in excavations or upon increase in moisture content. Determine potential problem and location of possible preconsolidated strata from available information. Examine roadways founded on geologic formations similar to those at site. Check condition of buildings and effects of rainfall and watering. Do seasonal ground water and rainfall or watering of shrubs or trees cause heave or settlement? Varved clays Pervious layers may cause more rapid settlement than anticipated. May appear to be unstable because of uncontrolled seepage flow through pervious layers between overconsolidated clay layers or may have weak clay layers. May be unstable in excavations unless well points are used to control ground water. Determine areas of possible varved clay deposits associated with prehistoric lakes. Determine settlement behavior of structures in the area. Check natural slopes and cuts for varved clays; check settlement behavior of structures. DG-1392, Appendix A, Page A-5 APPENDIX A,