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:
difficult to determine whether the results relate to unconsolidated-undrained, consolidated-undrained, consolidated-drained, or unconsolidated-drained conditions or to intermediate conditions between these DG-1392, Page 19 limiting states. Interpretation of in situ test results requires the complete evaluation of test conditions and limitations. Rock units commonly contain natural joints, bedding planes, or other discontinuities (e.g., faults and shear zones) that result in irregularly shaped blocks that respond as a discontinuum to various loading conditions. Individual solid blocks might have relatively high compressive and shear strengths, whereas strength along the discontinuity surfaces can be significantly lower and highly anisotropic. Commonly, little or no tensile strength exists across discontinuities. Large-scale in situ tests tend to average out effects of the complex interactions between intact rock blocks and discontinuities. In situ tests in rock are used to determine in situ stresses and deformation properties, including strength and deformation modulus of the jointed rock mass. These tests also help to determine strength and residual stresses along discontinuities in the rock mass. In situ testing performed in weak, near-surface rocks includes penetration tests, plate loading tests, pressure-meter tests, and field geophysical tests. Table F-2 in Appendix F lists in situ tests that are useful for determining the shear strength of subsurface materials. Direct shear-strength tests in rock measure peak and residual direct shear strength as a function of normal stress on the shear plane. Direct shear strength from intact rock can be measured in the laboratory if the specimen can be cut and transported without disturbance. In situ shear tests are discussed and compared by Nicholson (1983; Ref. 20) and Bowles (1996; Ref. 21). The suggested in situ method for determining direct shear strength of rocks is described in RTH 321-80, “Suggested Method for In