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Attenuation relationships were used to predict both PGA and spectral acceleration response content of each type of earthquake. Once the PGA and spectral response of the ground motions were determined, time history records of like events were selected for use in the dynamic ground response analysis. An effort was made to match distance, magnitude, spectral content and PGA for all input time histories with those of the predicted values, though the inherent variability in earthquakes motions do not allow for complete agreement with the smoothed spectra provided from the regression analyses on which the attenuation relationships are based. 8.4.1 Summary of Recent Seismic Hazard Investigations Comparisons were made between the recommendations of the PGA on soil and rock from the following sources: (1) the Geomatrix (1995) report to the ODOT titled, Seismic Design Mapping of the <strong>State</strong> of <strong>Oregon</strong>, (2) the USGS’s National Seismic Mapping Project (USGS 2000), and (3) the URS Greiner/Woodward Clyde Portland Microzonation Maps (Wong et al. 2000). These recommendations are based on probabilistic, uniform hazard studies that combined the ground shaking contributions from the interplate, intraplate, and crustal earthquake scenarios, respectively, into one peak ground acceleration value for a given return period (Table 8.3). It should be noted that investigations by Geomatrix and the USGS provide recommendations for PGA on bedrock. The URS Greiner/Woodward Clyde report yields PGA values at the soil surface. The recommendations put forth in the URS Greiner/Woodward Clyde report, specifically the Portland area fault map shown in Figure 8.3, were incorporated into this demonstration application for the sake of completeness. Table 8.3: Comparison of Recommended PGA Values for the Site GROUND MOTIONS ASSOCIATED WITH SPECIFIED PROBABILITIES OF EXCEEDANCE PGA ROCK PGA soil SOURCE 10% in 50 Years 2% in 50 Years 10% in 50 Years 2% in 50 Years USGS 0.19g 0.38g N/A N/A Geomatrix 0.19g 0.37g N/A N/A URS Greiner / Woodward Clyde N/A N/A 0.20g – 0.25g 0.40g The peak ground accelerations provided by the seismic hazard studies referenced here reflect the contributions of all seismic sources in the region. These investigations yield uniform hazard data in that the value of peak horizontal acceleration for a given exposure time represents the combined, or “aggregate” hazard. The acceleration values cannot be directly attributed to a single source zone or single earthquake of given magnitude. For many seismic analyses in geotechnical and structural engineering, the earthquake magnitude is requisite input data. This is particularly important for analysis methods that incorporate the duration of ground motions, the number of significant cycles of shaking, or seismic energy. Soil liquefaction can be thought of as a fatigue failure of soils; therefore, the intensity of the shaking and number of loading cycles are necessary parameters in hazard evaluation. In order to use the acceleration values from hazard studies a de-aggregation of the hazard associated with individual seismic sources is required, to estimate the relative contribution of each seismic source and size of earthquake. This information is available for the seismic hazard studies presented by Geomatrix and the USGS. 151
8.4.2 Subduction Zone Bedrock Motions Ground motion characteristics were estimated for M w 8.5 and M w 9.0 subduction zone earthquakes with a source-to-site distance of 85 km. The M w 8.5 earthquake was chosen based on the recommendations published by Geomatrix (1995), and the M w 9.0 was recommended by Wong et al. (2000). The PGA rock was 0.12g and 0.14g for the M w 8.5 and M w 9.0 earthquakes, respectively, using an attenuation relationship created by Youngs et al. (1997). Recorded time histories from the M w 8.5, 1985 Michoacán earthquake (Aeropuerto station) and the M w 8.5, 1978 Miyagi-Oki (Ofunato station) subduction zone earthquakes were compared against the predicted target spectra, as shown in Figures 8.6 and 8.7. Durations were on the order of 60-70 seconds. The selected records provide a satisfactory match of spectral content and were used as the design input bedrock ground motions for the dynamic ground motion analysis, after scaling to the appropriate PGA rock values of 0.12g and 0.14g. The predicted earthquake parameters are shown in Table 8.4 and the selected time history data is shown in Table 8.5. The intraplate earthquake was not considered in the analyses because the interplate and crustal earthquake scenarios would sufficiently “bracket” the seismic hazard. 1.50 1.40 1.30 1.20 1.10 (5% Damping) Magnitude 8.5 Target Spectrum Scaled Aeropuerto Ground Motion Scaled Ofunato Ground Motion Spectral Acceleration (g) 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0 0.5 1 1.5 2 2.5 3 Period (sec) Figure 8.6: Aeropuerto and Ofunato (Scaled PGA = 0.12g) Response Spectra Compared to the Magnitude 8.5 Cascadia Subduction Zone Target Spectrum on Rock 152
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ASSESSMENT AND MITIGATION OF LIQUEF
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ACKNOWLEDGMENTS The authors would l
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ASSESSMENT AND MITIGATION OF LIQUEF
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8.0 HAZARD EVALUATION AND DEVELOPME
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LIST OF FIGURES Figure 1.1: ODOT’
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Figure 8.8: Long Valley Dam and Lak
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Design of a given component shall l
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Liquefaction Mitigation Procedure G
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Pacific Northwest also are summariz
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2.0 OVERVIEW OF LIQUEFACTION-INDUCE
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oughly 50 centimeters, with numerou
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supported bridges along the Seward
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Another area of extensive bridge da
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Nineteen bridges were also damaged
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1. No foundation failures were obse
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piles supporting the fourth pier, l
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Figure 2.17: Observed Pile Deformat
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Figure 2.19: Damage from the 1906 S
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Figure 2.22: Ground Deformations Ne
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induced ground displacement was the
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Well-documented case histories of t
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Similar damage to pile foundations
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Examples of acceptable bridge found
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Numerous investigations of liquefac
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3.0 EVALUATION OF LIQUEFACTION SUSC
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The evaluation of liquefaction haza
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Table 3.1: Estimated Susceptibility
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movements, or localized ground disp
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Shear wave velocities can now be ob
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3.4 LIQUEFACTION RESISTANCE: EMPIRI
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Figure 3.1: Range of r d Values for
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The earthquake-induced shearing str
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drill rod during hammer impact. In
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Figure 3.5: Minimum Values for K σ
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3.4.2.2.1 CPT Method Developed by R
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1. Sensitive, fine grained 6. Sands
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Figure 3.9: CPT-Based Curves for Va
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CRR where: q c 2 3 0.00128 0.0
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Tacoma, Washington (Dickenson and B
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Table 3.8: Influence of OCR on the
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Figure 3.13: Influence of Fines Con
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Gravel Sand Figure 3.16: Relationsh
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FS L > 1.4: Excess pore pressure ge
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The post-liquefaction strength of s
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Figure 4.3: Undrained Critical Stre
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4.3 INTRODUCTION TO MODES OF FAILUR
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Figure 4.5: (a) Relationship betwee
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not available for many case studies
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provided to give the recommended ra
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Figure 4.8: Overview of EPOLLS Mode
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Figure 4.10: Model of Hypothetical
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4.5.2 Advanced Numerical Modeling o
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Figure 4.12: Post Volumetric Shear
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The relationship shown in Figure 4.
Page 114 and 115: A third type of failure is shown in
Page 116 and 117: Table 5.1: Liquefaction Remediation
Page 118 and 119: 5.3 DESIGN OF SOIL MITIGATION The d
Page 120 and 121: soil improvement guidelines state t
Page 122 and 123: The models were instrumented with a
Page 124 and 125: The model uses an explicit method,
Page 126 and 127: A simplification was made in the mo
Page 128 and 129: permanent earthquake displacements)
Page 130 and 131: 7.0 DEFORMATION ANALYSIS OF EMBANKM
Page 132 and 133: engineers; (2) requisite input incl
Page 134 and 135: π g 2 a t I a 2 dt (7-1) The A
Page 136 and 137: 10 1 Bracketed Intensity (m/s) 0.1
Page 138 and 139: 7.3 PARAMETRIC STUDY A well-validat
Page 140 and 141: the rigid body methods. The point a
Page 142 and 143: 0.4 Acceleration (g) 0.2 0 -0.2 -0.
Page 144 and 145: Embankment Height (m) Depth of Liqu
Page 146 and 147: 10 1 DISPLACEMENT (m) 0.1 Morgan Hi
Page 148 and 149: 2.0 Embankment Toe Embankment Mid-S
Page 150: suitably reliable estimates of perm
Page 153 and 154: interest. Specifically, the peak be
Page 155 and 156: Flow Chart for Evaluation and Mitig
Page 157 and 158: The deformation evaluations were pe
Page 159 and 160: Portland (a) (b) Figure 8.2: Illust
Page 161 and 162: Figure 8.4: Contours of PGA on Rock
Page 163: Borehole 4E CPT Hole 4E 26.0' NGVD
Page 167 and 168: 154 Table 8.5: Selected Acceleratio
Page 169 and 170: Spectral Acceleration (g) 1.50 1.40
Page 171 and 172: with the calculated equivalent unif
Page 173 and 174: n ( M 10 1) (8-1) where M is the
Page 175 and 176: 0.20 0.15 0.10 Acceleration (g) 0.0
Page 177 and 178: 15.0 12.5 10.0 Long Valley Dam Lake
Page 179 and 180: CSR should be modified for the pres
Page 181 and 182: 8.7 EVALUATION OF INITIATION OF LIQ
Page 183 and 184: crest stage Marine Drive 42.5 ft NG
Page 185 and 186: Table 8.9: Fines Content Values Est
Page 187 and 188: large sliding and long-term disrupt
Page 189 and 190: Table 8.12: Deformation Results fro
Page 191 and 192: The earthquake time histories used
Page 193 and 194: North (river) South (land) North To
Page 195 and 196: Table 8.20: Riverward Deformation R
Page 197 and 198: applications (DDC, closely spaced v
Page 199 and 200: Table 8.21: Comparison of Predicted
Page 202 and 203: 9.0 SUMMARY AND CONCLUSIONS Recent
Page 204: dewatering may be warranted. Additi
Page 207 and 208: Bardet, J.P. (1990). “LINOS - A N
Page 209 and 210: California Division of Mines and Ge
Page 211 and 212: Fujii, S., M. Cubrinovski, K. Tokim
Page 213 and 214: Ishihara, K. and M. Cubrinovski. (1
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Liu, A.H. and J.P. Stewart. (1999).
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Oregon Department of Transportation
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Schnabel, P., J. Lysmer, and H.B. S
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Sun, I.H. and I.M. Idriss. (1992).
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Youd, T.L. and C.F. Jones. (1993).
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