Structural Engineering & Earthquake Simulation Lab oratory 1 SG-1: Lateral Spreading – SG-1: Lateral Spreading – Observations and Analysis Observations and Analysis Raghudeep B., and S. Thevanayagam, UB Raghudeep B., and S. Thevanayagam, UB Aug. 07, 2007, 2-4 pm; UB-VTC Aug. 07, 2007, 2-4 pm; UB-VTC PI: R. Dobry, co-PI’s: A. Elgamal, S. Thevanayagam, T. Abdoun, M. Zeghal UB-NEES Lab: A. Reinhorn, M. Pitman, J. Hanley, SEESL-Staff Tulane: Usama El Shamy Students & Staff: UB (N. Ecemis, B. Raghudeep) and RPI (J. Ubilla, M. Gonzalez, V. Bennett, C. Medina, Hassan, Inthuorn)
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1 SG-1: Lateral Spreading – Observations and Analysis Raghudeep B., and S. Thevanayagam, UB Aug. 07, 2007, 2-4 pm; UB-VTC SG-1: Lateral Spreading – Observations.
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PI: R. Dobry, co-PI’s: A. Elgamal, S. Thevanayagam, T. Abdoun, M. ZeghalUB-NEES Lab: A. Reinhorn, M. Pitman, J. Hanley, SEESL-StaffTulane: Usama El ShamyStudents & Staff: UB (N. Ecemis, B. Raghudeep) and RPI (J. Ubilla, M. Gonzalez, V. Bennett, C. Medina, Hassan, Inthuorn)
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OutlineOutline
Review of Test SG-1 Lateral Spreading Observations & Animation Reanalysis of Lateral Spreading
o Initiation of spreading – hypothesis
o Newmark analysis - Sliding
o Some thoughts
Comparisons of LG-0 and SG-1o Highlights – Similarities & Differences (flat versus
sloping ground)
Thoughts on lateral spreading
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Review of Test SG-1Review of Test SG-1
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Review of Test SG-1Review of Test SG-1• Inclined Box (2o)
• Hydraulic Fill (Dr~50~55%)
• 18 ft Deep Saturated Sand
• Dense Instrumentation
• Design Base Motion (5s/10s/10s/10s)
• Uninterrupted Base Motion (5s ~0.01g/3s ~0.05g)
• Soil Liquefied
• Large lateral spreading observed
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Test SG-1 ConfigurationTest SG-1 ConfigurationTop View
• Yield Acceleration obtained from the available shear strength data which in turn is obtained from the pore pressure data.• = 22o is assumed.• Double-integration of relative acceleration to obtain displacement.
A closer look at previous slideA closer look at previous slide• At depth ~ 6.3ft, in LG0, the stress oscillates about zero shear stress.
• In SG1, due to the static shear stress (sloping ground), the stress path is shifted up closer to the failure envelope ( = 22o) which causes rapid build up of strain.
This Fig. clearly explains why soil in SG1 degraded faster than in LG0
0 5 10 15 20-5
0
5Stress Path comparison between LG0 & SG1
'v [kPa]
[k
Pa
]
0-5s LG00-5s SG1 Failure Envelope
Failure Envelope
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Cyclic Shear StrainsCyclic Shear Strains
-1
0
1Cyclic Shear Strains in LG0
cyc
at 0.5ft
-1
0
1cyc
at 6.25ft
-1
0
1
cyc [%
] cyc
at 8.75ft
-1
0
1cyc
at 11ft
0 1 2 3 4 5 6 7 8-1
0
1
Time [s]
cyc
at 15ft
-1
0
1Cyclic Shear Strains in SG1
cyc
at 0.4ft
-1
0
1cyc
at 6.35ft
-1
0
1
cyc [%
]
cyc
at 8.9ft
-1
0
1
cyc
at 11.05ft
0 1 2 3 4 5 6 7 8-1
0
1
Time [s]
cyc
at 15.25ft
Significantly cyclic in nature Monotonic Strains dominate
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Shear StressesShear Stresses
-3-1135
Shear Stresses in LG0
at 0.5ft
-3-1135
at 6.25ft
-3-1135
[k
Pa
] at 8.75ft
-3-1135
at 11ft
0 1 2 3 4 5 6 7 8-3-1135
Time [s]
at 15ft
-3-1135
Shear Stresses in SG1
at 0.4ft
-3-1135
at 6.35ft
-3-1135
[k
Pa
]
at 8.9ft
-3-1135
at 11.05ft
0 1 2 3 4 5 6 7 8-3-1135
Time [s]
at 15.25ft
Propagation of shear stresses in SG-1 diminishes with faster soil degradation
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Stress-Strain BehaviorStress-Strain Behavior
-3-1135
Stress-Strain Behavior in LG0
- 0-5s>5s d = 0.5ft
-3-1135
- 0-5s>5s d = 6.25ft
-3-1135
[k
Pa
]
- 0-5s>5s d = 8.75ft
-3-1135
- 0-5s>5s d = 11ft
0 3 6 9 12-3-1135
[%]
- 0-5s>5s d = 15ft
-3-1135
Stress-Strain Behavior in SG1
- 0-5s>5s d = 0.4ft
-3-1135
- 0-5s>5s d = 6.35ft
-3-1135
[k
Pa
]
- 0-5s>5s d = 8.9ft
-3-1135
- 0-5s>5s d = 11.05ft
0 3 6 9 12-3-1135
[%]
- 0-5s>5s d = 15.25ft
Small Deformations
Large Deformations, primarily initiated by graviational static shear
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Comments on LG-0 Vs SG-1Comments on LG-0 Vs SG-1
Initial Static shear stress plays an important role Soil degraded faster in SG-1 compared to LG-
0 Mostly Cyclic Strains in LG-0; Monotonic
strains dominate in SG-1 Level Ground Soil Strains accumulate @ high ru ~ 0.9-1.0.