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:
annular rock core with deformation meter. Diameters (usually 3) are measured before and after overcoring. Rock modulus is measured by laboratory tests on core; in situ stresses are computed by elastic theory. Measurement of absolute stresses in situ. Stress field is affected by borehole. Analysis subject to limitations of elastic theory. Two boreholes at different orientations are required for determination of complete stress field. Questionable results in rocks with strongly time-dependent properties. DG-1392, Appendix C, Page C-6 APPENDIX C, Cont’d. METHOD PROCEDURE APPLICABILITY LIMITATIONS Inclusion stressmeter Rigid stress-indicating device (stressmeter) is placed in borehole, and the hole is overcored to relieve stresses on annular core with stress meter. In situ stresses are computed by elastic theory. Measurement of absolute stresses in situ. Does not require accurate knowledge of rock modulus. Same as above. Borehole strain gauge Strain gauge is cemented to bottom of borehole, and gauge is overcored to relieve stresses on core containing strain gauge. Stresses are computed from resulting strains and from modulus obtained by laboratory tests on core. Measurement of one component of normal stress in situ. Does not require knowledge of rock modulus. Stress field affected by excavation or tunnel used. Interpretation of test results subject to assumption that loading and unloading moduli are equal. Questionable results in rock with strongly time-dependent properties. Hydraulic fracturing test Fluid is pumped into sealed-off portion of borehole with pressure increasing until fracture occurs. Estimation of minor principal stress. Affected by anisotropy of tensile strength in rock. Crosshole seismic test Seismic signal is transmitted from source in one borehole to receiver(s) in other borehole(s), and transit time is recorded. In situ measurement of compression wave velocity and shear wave velocity in soils and rocks. Requires deviation survey of boreholes to