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Structural Engineering & Earthquake Simulation Laboratory
1
SG-1: Lateral Spreading – SG-1: Lateral Spreading – Observations and AnalysisObservations and Analysis
Raghudeep B., and S. Thevanayagam, UBRaghudeep B., and S. Thevanayagam, UB
Aug. 07, 2007, 2-4 pm; UB-VTCAug. 07, 2007, 2-4 pm; UB-VTC
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)
2
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
3
Review of Test SG-1Review of Test SG-1
4
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
5
Test SG-1 ConfigurationTest SG-1 ConfigurationTop View
Side View
6
Input Base MotionInput Base Motion
14 16 18 20 22 24 26 28-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
Time [s]
Hor
izon
tal D
ispl
acem
ent [
in]
pol1x 17.8ft - Tied to the Base Shaker
1st Stage Motion
Damped Motion
Actuator Cut-Off
Data Analyzed in this Range
2nd Stage Motion2 Hz
7
Acceleration ResponseAcceleration Response
14 16 18 20 22-0.2
-0.1
0
0.1
0.2X-Motion of the Base
b1x
14 16 18 20 22-0.2
-0.1
0
0.1
0.2
Acc
ele
ratio
n [g
] b2x
14 16 18 20 22-0.2
-0.1
0
0.1
0.2
Time [s]
b3x
14 16 18 20 22-0.2
-0.1
0
0.1
0.2Y-Motion of the Base
b1y
14 16 18 20 22-0.2
-0.1
0
0.1
0.2b2y
14 16 18 20 22-0.2
-0.1
0
0.1
0.2
Time [s]
b3y
Base Input Motion
8
Excess Pore Pressure ResponseExcess Pore Pressure Response
0 10 20 30 40 50
0
2
4
6
8
10
12
14
16
18
Average Pore Pressure Profile
Excess Pore Pressure [kPa]
De
pth
[ft]
t = 19st = 20st = 21st = 22st = 22.5slimit
0 0.2 0.4 0.6 0.8 1
0
2
4
6
8
10
12
14
16
18
Average ru Profile
De
pth
[ft]
ru
t = 19st = 20st = 21st = 22st = 22.5s
9
Displacements (Potentiometers)Displacements (Potentiometers)
0
10
20POL22X at 0ft d
x-vertex17
0
10
20POL16X at 5.1ft d
x-vertex13
0
10
20
Ho
rizo
nta
l Dis
pla
cem
en
t [in
]
POL10X at 10.2ft dx-vertex7
0
10
20POL5X at 14.4ft d
x-vertex4
14 15 16 17 18 19 20 21 22
0
10
20
Time [s]
POL3X at 16.1ft dx-vertex3
0 5 10 15
0
2
4
6
8
10
12
14
16
18
Horizontal Displacement [in]
De
pth
[ft]
t = 19st = 20st = 21st = 22st = 22.5s
10
Shear Strains (potentiometer)Shear Strains (potentiometer)
14 15 16 17 18 19 20 21 220
5
10
15Shear Strain History for 1 - 13 Rings
Time [s]
glob
al [%
]
L#1-3 at 16.95ftL#3-5 at 15.25ftL#5-8 at 13.15ftL#8-10 at 11.05ftL#10-13 at 8.9ft
14 15 16 17 18 19 20 21 220
1
2
3
4
5
6Shear Strain History for 13 - 24 Rings
Time [s]
glob
al [%
]
L#13-16 at 6.35ftL#16-18 at 4.25ftL#18-20 at 2.55ftL#20-21 at 1.25ftL#21-23 at 0.4ft
cyc
ceases and continues
as monotonic shear
cyc
still exists
Top Rings
Bottom Rings
Delayed Initiation of Spread
Spread Initiation
11
Acceleration & PWP ResponseAcceleration & PWP Response
Ring Accelerations
Top
Middle
Bottom
14 16 18 20 22-0.1
0
0.1
0
0.5
1
14 16 18 20 22-0.1
0
0.1
0
0.5
1
14 16 18 20 22-0.1
0
0.1
Acc
ele
ratio
n [g
]
0
0.5
1
r u
14 16 18 20 22-0.1
0
0.1
0
0.5
1
14 16 18 20 22-0.1
0
0.1
Time [s]14 16 18 20 22
0
0.5
1
------ ru
____ acc 1.7ft
------ ru
------ ru
------ ru
------ ru
____ acc 5.1ft
____ acc 10.2ft
____ acc 14.4ft
____ acc 16.1ft
12
Lateral Spreading Observations Lateral Spreading Observations & Animation& Animation
13
VelocityVelocity
19 19.5 20 20.5 21 21.5 22 22.5-2
-1
0
1
2
3
4
5
6
7
8
Time [s]
Vel
ocity
[in/
s]
L#1 BaseL#16 at 5.1 ftL#18 at 3.4 ftL#20 at 1.7 ftL#21 at 0.8 ftL#23 at -0.8 ft
Rings stop following thebase ~ 19.5s
0 – 7ft
14
Velocity (Contd.)Velocity (Contd.)
19 19.5 20 20.5 21 21.5 22 22.5-2
-1
0
1
2
3
4
5
6
7
8
Time [s]
Vel
ocity
[in/
s]
L#1 BaseL#8 at 11.9 ftL#10 at 10.2 ftL#13 at 7.6 ft
Rings stop following the base ~ 20s
10 – 13ft
15
Velocity (Contd.)Velocity (Contd.)
19 19.5 20 20.5 21 21.5 22 22.5-2
-1
0
1
2
3
4
5
6
7
8
Time [s]
Vel
ocity
[in/
s]
L#1 BaseL#3 at 16.1 ftL#5 at 14.4 ft
Rings stop following the base ~ 20.5s
10 – 17ft
16
Velocity: ObservationsVelocity: Observations
• Spreading Initiation• Top 0 – 7ft ~ 19.5s• Middle 7 – 10ft ~ 20s• Bottom 10 – 17ft ~ 20.5s
• Each spread – 1 cycle apart & coincides with peaks.
• Parting velocity begins when the base turns ‘up-slope’ & when soil could not follow the base
• Bottom soil shows Newmark type response
17
Visualization SG1 (17.5~21.5s, x10)Pore Pressure Shear Strain
18
Reanalysis of Lateral SpreadingReanalysis of Lateral Spreading
Initiation of Spreading - HypothesisInitiation of Spreading - Hypothesis
19
Strain ProfileStrain Profile
-2 0 2 4 6 8 10 12 14
0
2
4
6
8
10
12
14
16
18
global
[%]
Dep
th [f
t]
t = 18st = 18.5st = 19st = 19.5st = 20st = 20.5st = 21st = 21.5st = 22st = 22.5s
Change of color to red in theprevious plot ~ 20s at 6.35ft
2nd color change between 20 - 20.5s at 14.4ft
Red Color Spreading upand down from 6.35ft
20
Velocity ProfileVelocity Profile
-1 0 1 2 3 4 5 6 7 8
0
2
4
6
8
10
12
14
16
18
Velocity [in/s]
Dep
th [f
t]
t = 18st = 18.5st = 19st = 19.5st = 20st = 20.5st = 21st = 21.5st = 22st = 22.5s
1st Seperation
2nd
3rd
21
Deduced Shear StressesDeduced Shear Stresses
0
5d = 0.4 ft
0
5d = 1.25 ft
0
5
[k
Pa
] d = 2.55 ft
0
5d = 4.25 ft
14 15 16 17 18 19 20 21 220
5
Time [s]
d = 6.35 ft
0
5d = 8.9 ft
0
5d = 11.05 ft
0
5
[k
Pa
] d = 13.15 ft
0
5
d = 15.25 ft
14 15 16 17 18 19 20 21 220
5
Time [s]
d = 16.95 ft
Top Rings
0
5d = 0.4 ft
0
5d = 1.25 ft
0
5
[k
Pa
] d = 2.55 ft
0
5d = 4.25 ft
14 15 16 17 18 19 20 21 220
5
Time [s]
d = 6.35 ft
0
5d = 8.9 ft
0
5d = 11.05 ft
0
5
[k
Pa
] d = 13.15 ft
0
5
d = 15.25 ft
14 15 16 17 18 19 20 21 220
5
Time [s]
d = 16.95 ft
Bottom Rings
22
Strength Degradation & Dynamic Strength Degradation & Dynamic Induced Stresses: AnimationInduced Stresses: Animation
23
Strength Degradation & Dynamic Strength Degradation & Dynamic Induced StressesInduced Stresses
14 16 18 20 220
2
4Stress:Strength History
[k
Pa
]
Time [s]0 10 20
0
2
4
stress path
'v [kPa]
0 0.5 1 1.5 2 2.50
2
4stress-strain behavior
[k
Pa
]
[%]
; d = 2.55ftf; = 22o
Failur
e Env
elope
_____Stress -------- Strength
24
Strength Degradation: AnimationStrength Degradation: Animation
25
Strength Degradation: AnimationStrength Degradation: Animation
26
Strength DegradationStrength Degradation
0 10 20
0
2
4
6
8
10
12
14
16
18
Stress Vs Strength
[kPa]
Dep
th [f
t]
f : = 22o
0 0.5 1
0
2
4
6
8
10
12
14
16
18
Stress/Strength Ratio
/f
Dep
th [f
t]/
f
t(s) = 21Initiation of Large Strains ~ 20s
27
Newmark Rigid Sliding Displacement Newmark Rigid Sliding Displacement AnalysisAnalysis
Rigid Block
a1(t)
a2(t)
ai(t)
an(t)
an-1(t)
aavg(t)
Yield Acceleration
• 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.
tatata yieldavgrel
t
rel ddatd0
1
0
22
1
Original Laminar Box
28
Newmark Displacements Newmark Displacements (without dilation)(without dilation)
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft]
Newmark Analysis 1.7ft: =22o
POL20X 1.7ft
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft] Newmark Analysis 3.4ft
POL18X 3.4ft
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft] Newmark Analysis 5.1ft
POL16X 5.1ft
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft] Newmark Analysis 7.6ft
POL13X 7.6ft
Initiation of Spread Initiation of Spread
Initiation of Spread Initiation of Spread
= 22o
29
Newmark Displacements Newmark Displacements (with dilation)(with dilation)
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft]
Newmark Analysis 1.7ft: =26o
POL20X 1.7ft
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft] Newmark Analysis 3.4ft
POL18X 3.4ft
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft] Newmark Analysis 5.1ft
POL16X 5.1ft
14 16 18 20 22-0.5
0
0.5
1
1.5
2
2.5
Time [s]
Ho
rizo
nta
l Dis
pla
cem
en
t [ft] Newmark Analysis 7.6ft
POL13X 7.6ft
Initiation of Spread Initiation of Spread
Initiation of Spread Initiation of Spread
Lower Displacements
= 26o
Strain
30
Lateral Spreading - ThoughtsLateral Spreading - Thoughts
• Tentatively Newmark model agrees with initiation of sliding
• But over-predicts magnitude of spread
• Perhaps, dilation contributes to smaller spread than Newmark (w/o dilation)
• Tentatively, Newmark spreading decreases with inclusion of dilation (increase of frictional angle)
31
Level Ground versus Sloping GroundLevel Ground versus Sloping Ground
LG-0 Vs SG-1LG-0 Vs SG-1
32
Level Ground Vs Sloping GroundLevel Ground Vs Sloping Ground
• LG-0: No static shear
• SG-1: Non-Zero Static Shear
Influence of initial static shear on pwp development and shear strains – Discussed next
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
33
LG0 Vs SG1: AccelerationsLG0 Vs SG1: Accelerations
0 2 4 6 8-0.1
0
0.1
Accelerations & ru in LG0
0
0.5
1
0 2 4 6 8-0.1
0
0.1
0
0.5
1
0 2 4 6 8-0.1
0
0.1
Acc
ele
ratio
n [g
]
0
0.5
1
r u
0 2 4 6 8-0.1
0
0.1
0
0.5
1
0 2 4 6 8-0.1
0
0.1
Time [s]0 2 4 6 8
0
0.5
1
------ ru
____ acc 1ft
------ ru
------ ru
------ ru
------ ru
____ acc 5ft
____ acc 7.5ft
____ acc 10ft
____ acc 14ft
0 2 4 6 8-0.1
0
0.1
Accelerations & ru in SG1
0
0.5
1
0 2 4 6 8-0.1
0
0.1
0
0.5
1
0 2 4 6 8-0.1
0
0.1
Acc
ele
ratio
n [g
]
0
0.5
1
r u
0 2 4 6 8-0.1
0
0.1
0
0.5
1
0 2 4 6 8-0.1
0
0.1
Time [s]
0
0.5
1
------ ru
____ acc 0.8ft
------ ru
------ ru
------ ru
------ ru
____ acc 5.1ft
____ acc 7.6ft
____ acc 10.2ft
____ acc 14.4ft
Quick degradation of accelerations in SG-1 due to fast pwp development due to initial static shear
34
DisplacementsDisplacements
-505
1015
Potentiometers of LG0
POLS18X at 1ft
-505
1015
Potentiometers of SG1
POL21X at 0.8ft
-505
1015
POLS13X at 5ft
-505
1015
POL16X at 5.1ft
-505
1015
Ho
rizo
nta
l Dis
pla
cem
en
t [g
]
POLS10X at 7.5ft
-505
1015
POL13X at 7.6ft
-505
1015
POLS8X at 10ft
-505
1015
POL10X at 10.2ft
0 1 2 3 4 5 6 7 8-505
1015
Time [s]
POLS3X at 14ft
0 1 2 3 4 5 6 7 8-505
1015
Time [s]
POL5X at 14.4ft
35
Pore Pressure RatiosPore Pressure Ratios
0 0.2 0.4 0.6 0.8 1
0
2
4
6
8
10
12
14
16
18
Pore Pressure Ratio Evolution for LG0 test
ru
De
pth
[ft]
t = 0st = 2st = 4st = 5st = 6st = 7st = 8st = 8.5s
0 0.2 0.4 0.6 0.8 1
0
2
4
6
8
10
12
14
16
18
Pore Pressure Ratio Evolution for SG1 test
De
pth
[ft]
ru
Negligible ru during 5s (ND)
Faster pwp during 5s (ND)
36
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
37
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
38
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
39
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
40
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.
Sloping Ground Soil Strains accumulate @ low ru (~ 0.6-0.7)
41
ConclusionsConclusions• Unique & High Quality Large scale Lateral
Spreading Data is now available to study mechanism of lateral spreading
• Lateral Spreading begins before full liquefaction and spreads downward with soil degradation
• Newmark Sliding Block Approximation, coupled with strength degradation, appears to be a likely tool for lateral spreading analysis
• Dilation during lateral spreading may be a constraint against build up of spreading
• Initial static shear appears a distinct component in build up of pwp, strength degradation during shaking, and initiation of large lateral spreading
