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Liquefaction Mitigation Procedure Geo/Hydro Section evaluates liquefaction and approach fill deformation potential (lateral displacements and settlement) Typical Design No Large embankment STEP I deformation potential? Yes Foundation and Structural Designers determine damage potential to structure. STEP II Typical Design No Significant potential for damage to bridge? Yes STEP III Is structure located on a designated “Lifeline” route? Yes Yes No OTHER CRITERIA (for consideration) Document liquefaction & lateral spread damage potential and perform typical design No No ADT on or under bridge Economic Recovery Route Ratio of mitigation cost/current structure replacement cost Current bridge replacement cost Yes Does Structure Qualify for Mitigation? (Bridge Section Decision) Proceed with Mitigation Design STEP IV Figure 1.1: ODOT’s Liquefaction Mitigation Procedure 4
For the construction of new bridges, extensive field and laboratory tests may not be available when the alternative sites are under review. Also, relatively small structures of routine importance may not economically justify large-scale exploration, sampling, and laboratory testing programs. In these instances, the lack of requisite geotechnical data precludes rigorous analysis of seismic performance and more simplified approaches are warranted for planning and preliminary design. A primary objective of this project was to synthesize existing analysis procedures with advanced numerical modeling to develop simple, straightforward methods of estimating earthquake deformations on embankments for design applications where resources, or the importance of the structure, do not justify the use of sophisticated numerical models. The methods discussed can be considered screening tools for identifying vulnerable sites as well as preliminary design tools. The following objectives were developed for this project. 1. Review the technical literature and establish a database of case histories. 2. Provide a synopsis of the literature to evaluate liquefaction hazards with emphasis on the most widely adopted, standard-of-practice methods for use by ODOT engineers. 3. Evaluate the applicability of current standard-of-practice methods for deformation analyses for embankments. 4. Perform a suite of numerical dynamic effective stress analyses for comparison against the more routine sliding-block methods. 5. Develop recommendations for evaluating seismically-induced deformations of embankments at sites with or without soil improvement. 1.2.2 Scope of Work The scope of work for each of these objectives is outlined below. 1.2.2.1 Establish a Database of Case Histories An extensive technical literature search was conducted to collect case histories on the seismic performance of bridges in liquefiable soils. The literature review was used to evaluate the performance of bridges and appurtenant structures, and to determine the controlling variables used in design. The results of this review are contained in Chapter 2 and the Appendix. 1.2.2.2 Literature Synopsis to Evaluate Liquefaction Hazards Current methods for evaluating the liquefaction susceptibility of soils are based on field performance and laboratory testing of clean sand and silty sand. Recent workshops have addressed the strengths and limitations of these evaluation procedures as they apply to predominantly sandy soils. However, key issues remain unresolved. One issue is the dynamic behavior of predominantly silty soil. Silts are common in many regions of <strong>Oregon</strong> (along the Columbia and Willamette Rivers, Portland West Hills and adjoining regions, coastal regions of the state) and there was little data for characterizing the liquefaction resistance, or the post-liquefaction behavior of silty soils. For this objective, data was collected from the technical literature and laboratory research conducted on regional silts. The results of several extensive investigations on silty soils from the 5
Page 1: ASSESSMENT AND MITIGATION OF LIQUEF
Page 5 and 6: ACKNOWLEDGMENTS The authors would l
Page 7 and 8: ASSESSMENT AND MITIGATION OF LIQUEF
Page 9 and 10: 8.0 HAZARD EVALUATION AND DEVELOPME
Page 11 and 12: LIST OF FIGURES Figure 1.1: ODOT’
Page 13: Figure 8.8: Long Valley Dam and Lak
Page 16 and 17: Design of a given component shall l
Page 20 and 21: Pacific Northwest also are summariz
Page 23 and 24: 2.0 OVERVIEW OF LIQUEFACTION-INDUCE
Page 25 and 26: oughly 50 centimeters, with numerou
Page 27 and 28: supported bridges along the Seward
Page 29 and 30: Another area of extensive bridge da
Page 31 and 32: Nineteen bridges were also damaged
Page 33 and 34: 1. No foundation failures were obse
Page 35 and 36: piles supporting the fourth pier, l
Page 37 and 38: Figure 2.17: Observed Pile Deformat
Page 39 and 40: Figure 2.19: Damage from the 1906 S
Page 41 and 42: Figure 2.22: Ground Deformations Ne
Page 43 and 44: induced ground displacement was the
Page 45 and 46: Well-documented case histories of t
Page 47 and 48: Similar damage to pile foundations
Page 49 and 50: Examples of acceptable bridge found
Page 51 and 52: Numerous investigations of liquefac
Page 53 and 54: 3.0 EVALUATION OF LIQUEFACTION SUSC
Page 55 and 56: The evaluation of liquefaction haza
Page 57 and 58: Table 3.1: Estimated Susceptibility
Page 59 and 60: movements, or localized ground disp
Page 61 and 62: Shear wave velocities can now be ob
Page 63 and 64: 3.4 LIQUEFACTION RESISTANCE: EMPIRI
Page 65 and 66: Figure 3.1: Range of r d Values for
Page 67 and 68: 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.
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A third type of failure is shown in
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Table 5.1: Liquefaction Remediation
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5.3 DESIGN OF SOIL MITIGATION The d
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soil improvement guidelines state t
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The models were instrumented with a
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The model uses an explicit method,
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A simplification was made in the mo
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permanent earthquake displacements)
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7.0 DEFORMATION ANALYSIS OF EMBANKM
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engineers; (2) requisite input incl
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π g 2 a t I a 2 dt (7-1) The A
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10 1 Bracketed Intensity (m/s) 0.1
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7.3 PARAMETRIC STUDY A well-validat
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the rigid body methods. The point a
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0.4 Acceleration (g) 0.2 0 -0.2 -0.
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Embankment Height (m) Depth of Liqu
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10 1 DISPLACEMENT (m) 0.1 Morgan Hi
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2.0 Embankment Toe Embankment Mid-S
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suitably reliable estimates of perm
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interest. Specifically, the peak be
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Flow Chart for Evaluation and Mitig
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The deformation evaluations were pe
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Portland (a) (b) Figure 8.2: Illust
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Figure 8.4: Contours of PGA on Rock
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Borehole 4E CPT Hole 4E 26.0' NGVD
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8.4.2 Subduction Zone Bedrock Motio
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154 Table 8.5: Selected Acceleratio
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Spectral Acceleration (g) 1.50 1.40
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with the calculated equivalent unif
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n ( M 10 1) (8-1) where M is the
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0.20 0.15 0.10 Acceleration (g) 0.0
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15.0 12.5 10.0 Long Valley Dam Lake
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CSR should be modified for the pres
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8.7 EVALUATION OF INITIATION OF LIQ
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crest stage Marine Drive 42.5 ft NG
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Table 8.9: Fines Content Values Est
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large sliding and long-term disrupt
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Table 8.12: Deformation Results fro
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The earthquake time histories used
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North (river) South (land) North To
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Table 8.20: Riverward Deformation R
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applications (DDC, closely spaced v
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Table 8.21: Comparison of Predicted
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9.0 SUMMARY AND CONCLUSIONS Recent
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dewatering may be warranted. Additi
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Bardet, J.P. (1990). “LINOS - A N
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California Division of Mines and Ge
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Fujii, S., M. Cubrinovski, K. Tokim
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Ishihara, K. and M. Cubrinovski. (1
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Liu, A.H. and J.P. Stewart. (1999).
Page 217 and 218:
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).
Page 223:
Youd, T.L. and C.F. Jones. (1993).
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