Document: NRC Regulatory Guide
Document ID: 1859c547-c10c-4ce4-ad2e-e54f7b66d4ef
Document Type: regulatory_guide
Title: Laboratory Investigations of Soils and Rocks for Engineering Analysis and Design of Nuclear Power Plants + HISTORY – HISTORY 07/2014 – DG-1256 , Proposed Revision 3 08/2001 – DG-1109 , Proposed Revision 2 (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1318/ML13186A032.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.138
CFR Part: 
CFR Title: 

Content:
hould identify average test values of material properties as well as the range of values that identify their variability. In addition to the most representative samples, investigators should also test samples that have extreme properties and represent critical zones. For additional information, Regulatory Guide 1.132, “Site Investigations for Foundations of Nuclear Power Plants,” offers guidelines for spacing of borings and frequency of sampling. Additional boring and sampling may be required when laboratory examination of the samples reveals an inadequate number or distribution of suitable samples to meet testing requirements. DG-1256, Page 7 4.2. Undisturbed Samples a. Undisturbed test samples should be prepared to preserve the natural structure and water content of the material. The sample should always be prepared in a humid room. Trimming instruments should be sharp and clean and the sample adequately supported. b. Investigators should examine undisturbed tube samples of soils for evidence of disturbance. A serious source of damage to undisturbed soil samples is the extrusion of the samples from the sample tubes. One method that may minimize damage during the removal of samples from thin-wall tubes is to split the tube lengthwise by milling. Another method is to saw the tube transversely into segments of sufficient length to extrude a single test specimen from each and then trim off the ends. It is important, however, to consider the fact that milling may cause disturbance and changes in the void ratio in some soils, particularly in loose sand. Dressing the cut tube edges before extruding samples from the tube sections reduces disturbance of the sample. Reuse of thin-walled sample tubes is not recommended if they have been damaged in the process of retrieving or extruding samples. Undisturbed tube samples should satisfy the following criteria: (1) The specific recovery ratio should be between 90 and 100 percent; a tube with less recovery may be acceptable