Report - Oregon State Library: State Employee Information Center ...

More documents

Recommendations

Info

The post-liquefaction strength of silty soils has been investigated in the laboratory by cyclically loading the soil until r u = 100%, then monotonically loading the soil undrained. It is interesting to note that numerous investigators have found that liquefied silty sands and silts are dilative when sheared following liquefaction (Stark et al. 1997; Boulanger et al. 1998; Dickenson et al. 2000). This behavior indicates that once the soil liquefies, large strains can be mobilized at sloping sites and at large strain the strength of the soil increases. This scenario assumes that the loading is fully undrained. In light of the limitations associated with sampling cohesionless soils and laboratory testing of the postliquefaction behavior of soil, it is not recommended that the strength gain due to dilation be incorporated into design. 4.2.2.2 The Strength of Liquefied Sand from In Situ Test Data Recognizing the difficulties associated with laboratory testing of cohesionless soil, alternative methods have been proposed for evaluating the residual shear strength of a fully liquefied deposit. Two procedures that are commonly used are: (1) residual strength ratio methods (Stark and Mesri 1992; Baziar and Dobry 1995); and (2) a procedure which is independent of the in situ vertical effective stress (Seed and Harder 1990). The relationship between SPT data, (N 1 ) 60 , and residual shear strength (S r ) with vertical effective overburden pressure (σ′ vo ) for silty soil deposits developed by Baziar and Dobry (1995) is shown in Figure 4.2. The curves were developed from the back-calculation of residual shear strengths from case studies where liquefaction failures had occurred. Nearly all of the case histories were selected based on previous work by Stark and Mesri (1992). The evaluation procedure developed by Baziar and Dobry is based on the use of the SPT to evaluate the potential for large deformations during earthquakes in saturated loose sandy silt and silty sand deposits and slopes. The method is based on laboratory tests and case histories corresponding to earthquakes of less than M W 8.0. Charts relating the normalized standard penetration resistance and residual shear strength to vertical effective overburden pressure have been developed for use as screening tools in liquefaction hazard evaluations (Figure 4.2). Figure 4.2 can be used to evaluate the large ground deformation potential during earthquakes due to shearing of saturated, non-gravelly silt-sand deposits having at least 10% fines. The figure is applicable to slopes, embankments, and level or almost level sites prone to lateral spreading. Figure 4.2 suggests that silty soils with a measured (N 1 ) 60 versus σ′ vo profile plotting to the right of the chart cannot experience flow failure due to their dilative behavior, and that lateral spreading generally cannot exceed 0.3 to 1.0 m (1 to 3 ft) for earthquakes of less than M W 8.0. Figure 4.2(b) indicates that for silty deposits that have experienced large deformations or flow failures, the S r /σ′ vo ranges from about 0.04 to 0.20. The average value of S r /σ′ vo is 0.12. 78
Figure 4.2: Charts Relating (a) Normalized Standard Penetration Resistance (N 1 ) 60 ; and (b) Residual Shear Strength S r to Vertical Effective Overburden Pressure σ′ vo , for Saturated Nongravelly Silt-Sand Deposits that have Experienced Large Deformations (Baziar and Dobry 1995) Similar to Baziar and Dobry, Stark and Mesri (1992) related the normalized clean sand blowcount value, (N 1 ) 60 CS , to the residual undrained critical strength ratio for magnitude 7.5 earthquakes. As illustrated in Figure 4.3, the post-liquefaction strength of the soil is provided for two conditions: the yield strength and the critical strength. The steeper curve represents the yield, or mobilized undrained shear strength. The flatter curve represents the critical undrained shear strength curve. Stark and Mesri recommend that the yield curve be used only for cases where the post-cyclic shearing is drained. If the drainage conditions cannot be verified, the critical undrained shear strength curve should be used. 79
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 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
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 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
Page 108 and 109: 4.5.2 Advanced Numerical Modeling o
Page 110 and 111: Figure 4.12: Post Volumetric Shear
Page 112 and 113: 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 and 164:
Borehole 4E CPT Hole 4E 26.0' NGVD
Page 165 and 166:
8.4.2 Subduction Zone Bedrock Motio
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
Page 215 and 216:
Liu, A.H. and J.P. Stewart. (1999).
Page 217 and 218:
Oregon Department of Transportation
Page 219 and 220:
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).
show all

Report - Oregon State Library: State Employee Information Center ...

Create successful ePaper yourself

Delete template?

Save as template?