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
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CFR Title: 

Content:
to determine static strength. The dynamic testing program should include tests to determine the soil parameters needed as input for reference analyses and studies of soil structure interaction and to determine the dynamic strength characteristics and liquefaction potential of soils. For additional information, Appendix A lists some laboratory investigations and testing procedures for determining dynamic soil properties and soil behavior, with related references. Dynamic soil property testing includes cyclic triaxial tests and resonant column tests. 6.2. Cyclic Triaxial Tests a. Investigators should use laboratory cyclic tests only to establish parametric effects on cyclic strength behavior. Because test equipment is readily available and the preparation of undisturbed specimens is relatively easy, the most common cyclic loading technique for investigating liquefaction resistance historically has been the cyclic triaxial test—in spite of wide recognition of the test’s inability to accurately represent field earthquake stresses and boundary conditions (Seed and Idriss, 1982, Ref. 28). Other research studies have demonstrated that laboratory-determined cyclic triaxial strengths (in fact, strengths determined from any unidirectional loading test) are higher than those expected to produce equivalent effects in the field (Seed, 1976, Ref. 29). Research also has shown that estimation of field cyclic test results may not be possible by universal application of sample factors (e.g., gradation, density, and soil type) (Koester, 1992, Ref. 30). b. Since the cyclic triaxial test does not accurately model the stress conditions in situ, investigators should exercise caution when using laboratory-obtained soil cyclic strengths and should make appropriate downward adjustments of cyclic stress values obtained from triaxial tests, as required. Documentation should present and reference the rationale behind the adjustment and the data supporting its magnitude. For additional