Chapter 13 GEOTECHNICAL SEISMIC HAZARDS GEOTECHNICAL DESIGN MANUAL January 2019 Geotechnical Design Manual GEOTECHNICAL SEISMIC HAZARDS Table of Contents Section Page 13.1 Introduction ..................................................................................................... 13-1 13.2 Geotechnical Seismic Hazard Failure Modes .................................................. 13-2 13.2.1 Seismic Acceleration Hazards ............................................................. 13-2 13.2.2 Global Hazards ................................................................................... 13-3 13.3 Geotechnical Seismic Hazard Evaluation Process .......................................... 13-3 13.3.1 Seismic Shaking Evaluation Process .................................................. 13-4 13.3.2 Soil Shear Strength Loss Hazard Evaluation Process ......................... 13-4 13.4 Geotechnical Seismic Hazard Analytical Methodologies ................................. 13-7 13.5 Soil Shear Strength Loss Mechanisms ........................................................... 13-7 13.5.1 Cyclic Liquefaction of Sand-Like Soils ................................................. 13-8 13.5.2 Cyclic Softening of Clay-Like Soils ...................................................... 13-9 13.5.3 SC Historical Cyclic Liquefaction ......................................................... 13-9 13.6 Soil Shear Strength Loss Susceptibility Screening Criteria ........................... 13-12 13.6.1 Sand-Like Soil ................................................................................... 13-14 13.6.2 Normally Sensitive (NS) Clay-Like Soil .............................................. 13-16 13.6.3 Highly Sensitive (HS) Clay-Like Soil .................................................. 13-16 13.7 Soil Shear Strength Loss Triggering ............................................................. 13-16 13.8 Cyclic Stress Ratio (CSR) ............................................................................. 13-18 13.8.1 Equivalent Seismic-Induced Stress (CSReq) ...................................... 13-19 13.8.2 Magnitude Scaling Factor .................................................................. 13-21 13.9 Cyclic Resistance Ratio (CRR) ..................................................................... 13-22 13.9.1 Sand-Like Soil - SPT Based CRR* Curves ......................................... 13-25 13.9.2 Sand-Like Soil - CPTu Based CRR* Curves ...................................... 13-26 13.9.3 Clay-Like Soil CRR* Curves ............................................................... 13-28 13.9.4 High Overburden Correction (Kσ) ...................................................... 13-30 13.9.5 Age Correction Factor (KDR) .............................................................. 13-32 13.9.6 Static Shear Stress Ratio Correction Factor (Kα) ............................... 13-36 13.10 Soil Shear Strength for Seismic Analyses ..................................................... 13-44 13.10.1 Sand-Like Soil Cyclic Shear Strength Triggering ......................... 13-44 13.10.2 Sand-Like Soil Cyclic Liquefaction Shear Strength ...................... 13-46 13.10.3 Clay-Like Soil Cyclic Shear Strength Triggering .......................... 13-52 13.10.4 Clay-Like Soil Cyclic Softening Shear Strength ........................... 13-52 13.10.5 Seismic Soil Shear Strength Selection ........................................ 13-52 13.11 Flow Slide Failure ......................................................................................... 13-53 13.12 Seismic Acceleration Coefficients ................................................................. 13-54 13.13 Seismic Global Stability ................................................................................ 13-56 13.14 Newmark Seismic Displacement Methods .................................................... 13-58 13.14.1 Newmark Time History Analyses ................................................. 13-59 13.14.2 Simplified Newmark Charts ......................................................... 13-61 13.15 Seismic Soil Settlement ................................................................................ 13-63 13.15.1 Soil Characterization ................................................................... 13-64 13.15.2 Saturated Sand Settlement.......................................................... 13-64 13.16 References ................................................................................................... 13-69 January 2019 13-i Geotechnical Design Manual GEOTECHNICAL SEISMIC HAZARDS List of Tables Table Page Table 13-1, Global Hazard Instability Cases ............................................................... 13-2 Table 13-2, CRR Determination Based on Types of In-situ Testing .......................... 13-23 Table 13-3, Liquefaction Susceptibility of Sedimentary Deposits .............................. 13-33 Table 13-4, Simplified Kα Values for Sand-Like Soils ............................................... 13-41 Table 13-5, Simplified Kα Values for Clay-Like Soils ................................................ 13-44 Table 13-6, Sand-Like Shear Strengths.................................................................... 13-45 Table 13-7, Values of ∆N1,60-rl ................................................................................... 13-47 Table 13-8, Values of ∆qt,1,N,-rl................................................................................... 13-48 Table 13-9, Seismic Soil Shear Strength Selection .................................................. 13-53 Table 13-10, No Slope Stability Analysis Required ................................................... 13-57 13-ii January 2019 Geotechnical Design Manual GEOTECHNICAL SEISMIC HAZARDS List of Figures Figure Page Figure 13-1, Cyclic Liquefaction-Induced Seismic Geotechnical Hazards .................. 13-6 Figure 13-2, Sand Boil Crater - 1886 Charleston, SC Seismic Event .......................... 13-9 Figure 13-3, 1886 Liquefaction and Ground Deformations Sites .............................. 13-10 Figure 13-4, Coastal Plain Paleoliquefaction Study Sites ......................................... 13-11 Figure 13-5, SC Quaternary Liquefaction Areas ....................................................... 13-12 Figure 13-6, Liquefaction Susceptibility Based on Soil Plasticity .............................. 13-13 Figure 13-7, Transition from Sand-Like to Clay-Like behavior .................................. 13-14 Figure 13-8, Plasticity Chart – Sand-Like/Clay-Like Soils ......................................... 13-15 Figure 13-9, Variations of Shear Stress Reduction Coefficient, rd ............................. 13-20 Figure 13-10, Magnitude Scaling Factor (MSF) ........................................................ 13-22 Figure 13-11, Typical CRR Curve ............................................................................. 13-23 Figure 13-12, Field CRR-ξR Correlations Based on SPT and CPTu ......................... 13-24 * Figure 13-13, Variation in ∆N 1,60 With Fines Content ............................................... 13-25 Figure 13-14, SPT Liquefaction Triggering Correlation (CRR*) ................................. 13-26 Figure 13-15, Variation in ∆qc,1,N With Fines Content ................................................ 13-27 Figure 13-16, CPTu Liquefaction Triggering Correlation (CRR*) ............................... 13-28 * Figure 13-17, CRR Clay-Like – Shear Strength Correlation ..................................... 13-29 * Figure 13-18, CRR Clay-Like Soils – OCR Correlation ............................................ 13-30 Figure 13-19, High Overburden Correction (Kσ) (σ’vo > 1 tsf) .................................... 13-31 Figure 13-20, Sand-Like Soil Strength Gain With Age .............................................. 13-34 Figure 13-21, Relationship Between Strength Gain Factor and Time ....................... 13-34 * Figure 13-22, Variations of Kα with SPT Blow Count (N 1,60) ..................................... 13-39 Figure 13-23, Variations of Kα with CPT Tip Resistance (qc,1,N) ................................ 13-40 Figure 13-24, Kα versus (τs/SU)α=0 For Clay-Like Soil (NC Drammen Clay) ............... 13-42 Figure 13-25, Kα versus (τs/Su)α=0 For Clay-Like Soil (1 ≤ OCR ≤ 8) ......................... 13-43 Figure 13-26, Excess Pore Pressure Ratio - Liquefaction Triggering ........................ 13-45 Figure 13-27, Liquefied Shear Strength Ratio - SPT................................................. 13-47 Figure 13-28, Liquefied Shear Strength Ratio - CPTu Tip Resistance ...................... 13-48 Figure 13-29, Liquefied Shear Strength Ratio - SPT Blow Count.............................. 13-50 Figure 13-30, Liquefied Shear Strength Ratio - CPT Tip Resistance ........................ 13-51 Figure 13-31, Simplified Wave Scattering Scaling Factor ......................................... 13-55 Figure 13-32, Pseudo-Static Limit Equilibrium Analysis Slice ................................... 13-56 Figure 13-33, Newmark Sliding Block Method .......................................................... 13-59 Figure 13-34, Newmark Time History Analysis ......................................................... 13-60 Figure 13-35, Simplified Newmark Chart (PGV = 30 kmax in/sec) .............................. 13-62 Figure 13-36, Simplified Newmark Chart (PGV = 60 kmax in/sec) .............................. 13-62 ’ Figure 13-37, Volumetric Strain Relationship