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:
nits; evaluate intrusion of grout into the rock mass; distinguish and analyze fractures, shear zones, soft zones, cavities, and other discontinuities; and characterize water quality and flow. Borehole logging and crosshole shear-wave measurements are generally low-strain measurements. In rock, these measurements provide a suitable approximation of shear modulus even under high-strain conditions. In soil, the shear modulus depends strongly on strain level. Therefore, these methods are usually insufficient because nonlinear effects can occur that may lead to misinterpretation of the test results. Laboratory tests (e.g., resonant column torsional shear test) are more promising for shear modulus determination. DG-1392, Page 21 4.11 Logs of Subsurface Investigations It is important to have a complete and detailed log for every borehole. Boring logs should contain dates, locations, and depths of all borings, as well as elevations that are related to a permanent benchmark for the top and bottom of borings, boundaries of soil layers and rock units, and the level at which the water table was encountered. In addition, classification and description of soil layers and rock units, blow count values obtained from SPTs, percent recovery of rock core, quantity of core not recovered for each core interval or drill run, and rock quality designation should be noted. The factors that are needed for blow count correction, such as the type of sampler, hammer, and drill rod used in the SPT test, should also be recorded. Results of field permeability tests and geophysical borehole logging should be included on the logs. The type of tools used to make the boring should be recorded. Notes should be provided for everything significant to the interpretation of subsurface conditions, such as drilling rate, settling or dropping of drill rods, abnormally low resistance to drilling or advance of samplers, core loss, and instability or heave of the side and bottom of boreholes. Influx of ground