Document: NRC Regulatory Guide
Document ID: deae24ac-dab1-4d75-b025-d62d2bb88dd3
Document Type: regulatory_guide
Title: Procedures and Criteria for Assessing Seismic Soil Liquefaction at Nuclear Power Plant Sites
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1404/ML14041A345.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.198
CFR Part: 
CFR Title: 

Content:
Enclosure Regulatory Guide Periodic Review Regulatory Guide Number: 1.198 Title: Procedures and Criteria for Assessing Seismic Soil Liquefaction at Nuclear Power Plant Sites Office/Division/Branch: RES/DE/SGSEB Technical Lead: Thomas Weaver Recommended Staff Action: Reviewed with issues identified for future consideration 1. What are the known technical or regulatory issues with the current version of the RG? Since issuance of RG 1.198 in 2003 recent liquefaction research by Bray and Sancio (2006) and Boulanger and Idriss (2006) calls into question screening techniques for evaluating liquefaction potential of fine grained soils presented in the RG’s Discussion Section. These techniques are: “Cohesive soils with fines content greater than 30 percent and fines that either (i) are classified as clays based on the Unified Soil Classification (UCS) system or (ii) have a Plasticity Index (PI) greater than 30 percent should generally not be considered susceptible to liquefaction. “Other designations involving the “C” description, if the clay content is greater than 15 percent by weight and the liquid limit is greater than 35 percent and occurs at natural water contents lower than 90 percent can be considered nonliquefiable.” In addition, updated procedures for evaluating liquefaction potential have been proposed (Cetin et al. 2004, Moss et al. 2006, Boulanger and Idriss 2012). There are considerable differences in the newly proposed empirical methods, in part due to differing interpretations of the liquefaction case history database. The differences in interpretation need to be assessed. A National Research Council (NRC) study has been initiated to address the differences in the empirical models. This work needs to be completed prior to updating RG 1.198. The first draft of the NRC report is scheduled for September 2014 with a final report September 2015. While waiting for the National Research Council to address the case history database, the information in