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Other structures at this site supported by smaller pile groups or lightly reinforced piles, exhibited severe damage as shown in Figures 2.36 and 2.37. The Nadahama Bridge is visible in the background of Figure 2.36. Figure 2.36: Damage to Structures near the Nadahama Ohashi Bridge Figure 2.37: Damage to Pile Foundations near the Nadahama Ohashi Bridge 36
Numerous investigations of liquefaction-induced ground failures and bridge performance during the Kobe earthquake are still being conducted and more lessons will be learned. Some of the conclusions that have been gleaned from this earthquake are listed below. 1. Lateral spreading due to liquefaction can lead to span collapse even in modern structures with massive gravity foundations (caissons). 2. Foundations on soft ground, such as reclaimed land, are vulnerable to extensive damage due to the effect of liquefaction and lateral flow of ground. Piles can be subjected to large lateral pressures due to the flow of soil around the pile. 3. Most damage to embankments, levees and waterfront retaining structures, bridge abutments and pile foundations resulted from soil liquefaction and large inertial forces associated with strong ground motions. 4. In many cases, bridge piers supported by groups of large diameter steel pipe piles (more than 1 m in diameter) were not damaged despite extensive liquefaction and lateral spreading. At these same sites relatively small diameter, unreinforced piles (both steel pipe and precast concrete) suffered extensive damage under these conditions. 2.4 CONCLUSIONS The inventory of bridges in <strong>Oregon</strong> includes structures of widely varying vintage, design and construction, and materials. The review of bridge performance during past earthquakes provides relevant data for the evaluation of these bridges. Despite the diversity of bridge types, foundation schemes, seismic design principles, and construction techniques, it can be generalized that the seismic performance of bridges and ancillary components is influenced to a great degree by the behavior of the foundation soils during the earthquake. It is clear that liquefaction of soils beneath or near a highway embankment can lead to significant deformations and lateral loads on foundation elements. Damage to abutments and foundations underlain by loose- to mediumdense, saturated sands and silts has been reported for variety of foundation types (spread footings, light timber piles to heavy reinforced concrete piers, vertical and battered steel and concrete piles). It follows that foundation design must focus on minimizing seismic ground deformations in liquefiable and non-liquefiable soils to tolerable limits. This requirement can often only be accomplished with remedial ground treatment. A large collection of bridge performance data is provided in the Appendix to this report. A simplified damage-rating scheme has been applied for each case history in order to generally relate the displacements experienced by the bridge components and the extent of damage. Foundations resting on sandy soil with SPT N-values greater than 25 blows/ft experienced minimal damage provided they were compliant enough to withstand minimal lateral displacement. The improved foundation performance for piling embedded in gravels probably reflects the influence of the rapid dissipation of earthquake-induced pore pressures and the consequent prevention of ground failure. It should be noted, however, that liquefaction can occur in gravel where drainage is impeded by impervious layers. This phenomenon will be discussed in Chapter 3. The seismic design of bridge foundations along rivers, lakes and bays presents challenges due to the weak soils that are often prevalent in these environments. On the basis of the case histories, some general design considerations are listed below. 37
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 18 and 19: Liquefaction Mitigation Procedure G
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: Examples of acceptable bridge found
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
Page 69 and 70: drill rod during hammer impact. In
Page 71 and 72: Figure 3.5: Minimum Values for K σ
Page 73 and 74: 3.4.2.2.1 CPT Method Developed by R
Page 75 and 76: 1. Sensitive, fine grained 6. Sands
Page 77 and 78: Figure 3.9: CPT-Based Curves for Va
Page 79 and 80: CRR where: q c 2 3 0.00128 0.0
Page 81 and 82: Tacoma, Washington (Dickenson and B
Page 83 and 84: Table 3.8: Influence of OCR on the
Page 85 and 86: Figure 3.13: Influence of Fines Con
Page 87: Gravel Sand Figure 3.16: Relationsh
Page 90 and 91: FS L > 1.4: Excess pore pressure ge
Page 92 and 93: The post-liquefaction strength of s
Page 94 and 95: Figure 4.3: Undrained Critical Stre
Page 96 and 97: 4.3 INTRODUCTION TO MODES OF FAILUR
Page 98 and 99: Figure 4.5: (a) Relationship betwee
Page 100 and 101:
not available for many case studies
Page 102 and 103:
provided to give the recommended ra
Page 104 and 105:
Figure 4.8: Overview of EPOLLS Mode
Page 106 and 107:
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)
Page 130 and 131:
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
Page 138 and 139:
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.
Page 144 and 145:
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
Page 185 and 186:
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
Page 207 and 208:
Bardet, J.P. (1990). “LINOS - A N
Page 209 and 210:
California Division of Mines and Ge
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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).
Page 217 and 218:
Oregon Department of Transportation
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Schnabel, P., J. Lysmer, and H.B. S
Page 221 and 222:
Sun, I.H. and I.M. Idriss. (1992).
Page 223:
Youd, T.L. and C.F. Jones. (1993).
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