Design Standards No. 13 Embankment Dams Chapter 13: Seismic Analysis and Design Phase 4: Final U.S. Department of the Interior Bureau of Reclamation May 2015 Mission Statements The U.S. Department of the Interior protects America’s natural resources and heritage, honors our cultures and tribal communities, and supplies the energy to power our future. The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Design Standards Signature Sheet Design Standards No. 13 Embankment Dams DS-13(13)-8: Phase 4: Final May 2015 Chapter 13: Seismic Analysis and Design U.S. Department of the Interior Bureau of Reclamation May 2015 Foreword Purpose The Bureau of Reclamation (Reclamation) design standards present technical requirements and processes to enable design professionals to prepare design documents and reports necessary to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Compliance with these design standards assists in the development and improvement of Reclamation facilities in a way that protects the public's health, safety, and welfare; recognizes needs of all stakeholders; and achieves lasting value and functionality necessary for Reclamation facilities. Responsible designers accomplish this goal through compliance with these design standards and all other applicable technical codes, as well as incorporation of the stakeholders’ vision and values, that are then reflected in the constructed facilities. Application of Design Standards Reclamation design activities, whether performed by Reclamation or by a non-Reclamation entity, must be performed in accordance with established Reclamation design criteria and standards, and approved national design standards, if applicable. Exceptions to this requirement shall be in accordance with provisions of Reclamation Manual Policy, Performing Design and Construction Activities, FAC P03. In addition to these design standards, designers shall integrate sound engineering judgment, applicable national codes and design standards, site-specific technical considerations, and project-specific considerations to ensure suitable designs are produced that protect the public's investment and safety. Designers shall use the most current edition of national codes and design standards consistent with Reclamation design standards. Reclamation design standards may include exceptions to requirements of national codes and design standards. Proposed Revisions Reclamation designers should inform the Technical Service Center (TSC), via Reclamation’s Design Standards Website notification procedure, of any recommended updates or changes to Reclamation design standards to meet current and/or improved design practices. Chapter Signature Sheet Bureau of Reclamation Technical Service Center Design Standards No. 13 Embankment Dams Chapter 13: Seismic Analysis and Design DS-13(13)-8:1 Phase 4: Final May 2015 Chapter 13 – Seismic Analysis and Design is an existing chapter within Design Standards No. 13 and has been revised to include: A risk-informed approach to dam safety, consistent with policies of the Bureau of Reclamation Dam Safety Office Updated practices for: o assessment of liquefaction potential o strengths of foundation and embankment materials for assessing stability and deformation o analysis of deformation Additional information on seismic loadings and their use for dam-safety analysis Design features for new dams and modifications of existing dams 1 DS-13(13)-8 refers to Design Standards No. 13, chapter 13, revision 8. David Rees Gillette, Civil Engineer, Geotechnical Engineering Group 4, 86-68314 Peer Review ZcL5 Robert L. Dewey, P.E. Date Civil Engineer, Geotechn c Engineering Group 4, 86-68313 Security Review: 2x) Ashok Chugh, P.E. Date Civil Engineer, Geotechnical Engineering Group 1, 86-68311 Recommended for Technical Approval: ( sS—// Derek T. Wittwer, RE. Date Manager, Geotechnical Engineering Group 4, 86-68314 ed: Daniel W. Osmun, P.E. Chief, Geotechnical Services Division, 86-68300 Approved: Thomas A. Luebke, P.E. Date Director, Technical Service Center Abbreviations and Acronyms 1D one-dimensional 2D two-dimensional Amax peak horizontal acceleration at the ground surface ASTM American Society for Testing Materials atm atmospheric pressure BPT Hammer penetration tests CR Comprehensive Review CPT Cone Penetrometer Test CPTu CPT with measurement of pore-water pressure (u) CRR Cyclic Resistance Ratio CRRM=7.5,σ'=1 CRR normalized to standard magnitude and overburden CSR Cyclic Stress Ratio CSRM=7.5,σ'=1 CSR normalized to standard magnitude and overburden DCPT Dynamic Cone Penetration Test DSS Direct Simple Shear (Test) ECPT Electronic Cone Penetrometer Test FDM Finite Difference Method FEM Finite Element Method FS factor of safety g acceleration due to earth's gravity ICOLD International Commission on Large Dams LL liquid limit M earthquake magnitude MCE Maximum Credible Earthquake MSF Magnitude Scaling Factor (also known as DWF for duration weighting factor, or simply KM) MW earthquake moment magnitude NCEER National Center for Earthquake Engineering Research OSHA Occupational Safety and Health Administration PFM Potential Failure Mode PHA peak horizontal ground acceleration PI Plasticity Index PSHA Probabilistic Seismic Hazard Analysis Reclamation Bureau of Reclamation TSC Technical Service Center u pore-water pressure UHS uniform-hazard response spectra USCS Unified Soil Classification System USGS United States Geological Survey VS shear wave velocity VST Field Vane Shear Test Contents Page Chapter 13: Seismic Analysis and Design 13.1 Introduction ...................................................................................... 13-1 13.1.1 Applicability ..................................................................... 13-1 13.1.2 Deviations From Standard ................................................ 13-1 13.1.3 References ......................................................................... 13-1 13.1.4 Organization of This Chapter ............................................ 13-2 13.1.5 Definitions of Terms ......................................................... 13-2 13.2 Reclamation’s Approach to Seismic Analysis of Embankment Dams .......................................................................................... 13-5 13.2.1 Effects of Earthquakes on Embankment Dams ................ 13-5 13.2.2 Reclamation's Risk-Informed Dam Safety Decision Process ........................................................................ 13-6 13.2.3 Liquefaction, Cyclic Mobility, Cyclic Failure, and Cyclic Strain Potential ................................................ 13-7 13.2.4 General Sequence of Analysis .......................................... 13-8 13.2.5 Site Geology in Embankment Analysis .......................... 13-11 13.2.6 Uncertainty in Analyses .................................................. 13-11 13.3 Seismic Loadings for Analysis and Design ................................... 13-13 13.3.1 Current Reclamation Practice ......................................... 13-13 13.3.2 Products of Seismotectonic Studies ................................ 13-13 13.4 Investigations of Embankment and Foundation Materials ............ 13-14 13.4.1 Phased Exploration Philosophy ...................................... 13-14 13.4.2 General Sequence and Methods of Investigation............ 13-15 13.4.2.1 Search of Existing Information ...................... 13-15 13.4.2.1.1 File Data (Bureau of Reclamation) ......................... 13-15 13.4.2.1.2 File Data (Exteral) ..................... 13-16 13.4.2.1.3 Published Data ........................... 13-16 13.4.2.2 Surface Investigations .................................... 13-16 13.4.2.2.1 Ground Reconnaissance ............ 13-16 13.4.2.2.2 Surface Topographic and Geologic/Geotechnical Mapping ................................ 13-16 13.4.2.2.3 Surface Geophysics ................... 13-16 13.4.2.3 Subsurface Investigations ............................... 13-17 13.4.2.3.1 Test Pits/Test Trenches ............. 13-17 13.4.2.3.2 Electronic Cone Penetrometer Test Soundings ...................... 13-18 13.4.2.3.3 SPT ............................................ 13-19 13.4.2.3.4 BPT ............................................ 13-19 13.4.2.3.5 Borehole Geophysics ................. 13-20 13.4.2.3.6 Borehole Instrumentation .......... 13-20 DS-13(13)-8 May 2015 13-i Contents (continued) Page 13.4.2.3.7 Field Vane Shear Test ............... 13-20 13.4.2.4 Undisturbed Samples and Laboratory Shear Testing ............................................ 13-20 13.5 Dynamic Site Response ................................................................. 13-21 13.5.1 Introduction ..................................................................... 13-21 13.5.2 Dynamic Material Properties .......................................... 13-22 13.5.3 Seismic Loading.............................................................. 13-23 13.6 Evaluating Liquefaction Potential.................................................. 13-24 13.6.1 General ............................................................................ 13-24 13.6.2 Computing the CSR for Liquefaction Triggering Analysis..................................................................... 13-26 13.6.2.1 Basic Form and Equations .............................. 13-26