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:
actures, orientation, position, length and spacing of any other geologic discontinuities, surface infilling, and weathering. Rock outcrops may be one of the information sources necessary for rock mass characterization, especially for structures that require relatively shallow excavations. Core samples can also provide reliable information to define the engineering characteristics of the rock mass. Suitable coring methods should be employed, and rocks should be sampled to a depth below which rock characteristics do not influence foundation performance. Deeper borings may be needed to investigate zones critical to the evaluation of site geologic conditions. Within the depth intervals influencing foundation performance, zones of poor core recovery or low rock quality designation, zones requiring casing, and other zones where drilling difficulties are encountered should be investigated. The nature, geometry, and spacing of any discontinuities or anomalous zones should be determined by means of suitable logging or in situ observation methods, such as an in-hole camera or televiewer. Areas with evidence of significant residual stresses should be evaluated based on in situ stress or strain measurements. Dip and strike of bedding planes and joints in the near-surface region can be measured at the outcrop. However, oriented cores are needed to estimate dips and strikes at depth. A sufficient number of samples of both intact rock and jointed rock mass should be collected for strength property testing. The parameters developed from the rock mass characterization program provide input to different rock mass classification schemes (e.g., Rock Mass Rating system, Q system, Geological Strength Index system). The quality of the rock mass, estimated using the classification schemes, may be used in empirical design methods of rock excavation. 4.5.2 Sampling Coarse-Grained Soils For coarse-grained soils, samples should be taken at depth intervals no greater than 1.5 meters (5 feet).