Effective Stress Analysis to Evaluate Ejecta Severity at Sandy and Silty Soil Sites Daniel Hutabarat & Jonathan Bray University of California, Berkeley 2020 PEER Annual Meeting
Effective Stress Analysis to Evaluate Ejecta Severity at Sandy and Silty Soil Sites
Daniel Hutabarat & Jonathan BrayUniversity of California, Berkeley
2020 PEER Annual Meeting
Sediment Ejecta
1. Case Histories: 2010-2011 Canterbury EQsInconsistent assessment with current procedures
2. Physical Process: Back-AnalysisUse effective stress analyses to gain insight
3. Quantify its severityEjecta Potential Index (EPI)
Source: M. Cubrinovski (UC Canterbury)
2011 February Christchurch EQ
Underestimated CaseRrup: 4.7 kmPGA: 0.38 gEstimation: ModerateObservation: EXTREME
Mw 6.2 2011 February Christchurch
Overestimated CaseRrup: 5.7 kmPGA: 0.34 gEstimation: SevereObservation: NONE
Why?The sunk car
N/A
SCPT-57366BH-57258
LEGEND: Sand Ejecta
SCPT-57366BH-57258
SCPT-57366BH-57258
CPT-56473
SCPT-57345BH-57241
SCPT-57345BH-57241
CPT-45185
CPT-45184
CPT-45183
CPT-45185
CPT-45184
CPT-45183
Darfield (None)
ShirleyLSN: 3
Christchurch (Extreme) June (Severe)
Darfield (None) Christchurch (None) June (None)
ShirleyLSN: 15
ShirleyLSN: 6
St.TeresaLSN: 44
St.TeresaLSN: 46
St.TeresaLSN: 14
CPT-56473 CPT-56473
2010 Darfield EQ
Ejecta Observed
No Ejecta
van Ballegooy et al.Tonkin & Taylor
for the EQC
Ic = 1.8
qc (MPa) tip resistance Ic Soil Behavior Type Index
Dep
th (m
)
Occurrence of Liquefaction Ejecta Related to CPT Profile
7
48
๏ฟฝ๏ฟฝ
St. TeresaShirley
Dar
fCSR
June
CSR
Chc
hC
SR
June
CSR
Chc
hC
SRD
arfC
SR
Mw 6.0 June 13 , 2011 Christchurch Earthquake
https://youtu.be/rRVK5NJE2qEOriginal Video Duration: 3 mins 27 secLocation: Christchurch Suburb
Crust LayerImpermeable
Denser Layer(Fully Drained Soil)
H1
H2
Datum
โ
Depth be
low groun
d surface
LiquefieableLayer (Fully Drained Soil)
(a) Typical Soil Profile (b) โ , Total Head (m) (c) โ , Excess Head (m)
โexc
โp
โelv
Ejected Sediment
PiezometerA ho : Initial total head (Steady-state)
โexc
t = 0
โ โ โ โ
โ
G.W.L
Physical Process of Sediment Ejecta
H3
water flow
โ โ โcrack propagation G.W.L Raised
Deeper layer sustain the upward seepage flow during dissipation
๐๐๐๐ ๐๐๐๐Upward seepage-induced piping condition at the ground surface
Red Zone:
โ : Excess pressure head (m)โ : Critical head to cause piping condition (๐ ๐ at ground surface
Effective Stress Analysis (ESA)OpenSees v3.0
Crust
Shear stress time history ๐ ๐๐ขElastic half-space & outcrop motion
L-K (1969) Dashpot
Displacement and Pore Pressure Nodes
Solid-fluid saturated porous medium(u-p element)
Water level
Vertical Fixity
Equal DOF(tied nodes)
๐
1
2
๐
Saturated Nodes
Computed response(๐ข,๐ข,๐ข,๐)
Reduced Integration
SurfaceDry Nodes
At Corner:- ๐๐๐ ๐๐๐๐๐๐๐๐๐ก ๐ข- ๐ฃ๐๐๐๐๐๐ก๐ฆ ๐ข- ๐๐๐๐๐๐๐๐๐ก๐๐๐ ๐ข- ๐๐๐๐ ๐๐๐๐ ๐ ๐ข๐๐ ๐
At Center:- ๐ถ๐๐ - ๐พ
Stack of quad elementsSolve for
Constitutive Models
PM4Sand & PM4Silt(Boulanger & Ziotopoulou 2017,2018)
Based primarily on CPT data
For:๐ฉ : PM4Sand (Sand-Like)
๐ฉ : PM4Silt (๐ 0.99)
๐ฉ : PM4Silt (Clay-Like)
* Hutabarat & Bray PEER Report for more detail on PM4Sand & PM4Silt parameters
4 Key ParametersCPT Sounding
Soil Model
๐ ๐๐๐ occurred in red zone
โ
G.W.L
Artesian Flow Potential m ๐๐๐๐ ๐๐๐๐๐
๐ฎ๐พ๐ณ
๐ซ๐๐๐๐
๐ ๐
At each time step when ๐๐๐๐ ๐๐๐๐, the area is given by:
๐ ๐. ๐
๐๐, cause pipingProgressive cracks at crust
For thicker liquefaction,More RED Shaded AreaGreater Artesian PressureMore Water Volume
๐
Shirley St.Teresa
Base Motion Base Motion
Ejecta Potential Index (EPI)Artesian Flow Potential integrated over time
๐ธ๐๐ผ ๐3. ๐ ๐๐๐๐ ๐๐๐๐๐
๐ฎ๐พ๐ณ
๐ซ๐๐๐๐
๐ ๐ ๐ ๐๐๐
๐Measure of hydraulic gradient, critical layer thickness,
and volume of water over time
Extending the analysis duration is important to understand the full story
0.00.20.40.60.81.01.21.41.61.82.0
0 20 40 60 80 100 120 140 160 180
HBI
(m3 )
Time (sec)
Shirley Darfield StTeresa DarfieldShirley Christchurch StTeresa ChristchurchShirley June StTeresa June
EXTREME
SEVERE
NONE
Artesia
n Flow
Potential (m
3 )
Site Event LSN Observation EPI (m3.s)
ShirleyDarfield
3 NONE 0St.Teresa 44 NONE 0
ShirleyChristchurch
15 EXTREME 211St.Teresa 46 NONE 0
ShirleyJune
6 SEVERE 83St.Teresa 14 NONE 0
Evaluation of EPI
23 Well-investigated sites (BH, CPT, VsVp, GWL, Photos)
Well-documented case histories (22 New Zealand + 1 Japan)
4 Shallow-crustal earthquakes
0
50
100
150
200
250
300
350
400
0 5 10 15 20 25 30 35 40 45 50
Ejec
ta P
oten
tial I
ndex
Scenario #
Minor
Moderate
Severe
Extreme
3 Extreme : EPI >1206 Severe : 40 < EPI < 12010 Moderate : 10 < EPI < 403 Minor : 2 < EPI < 1024 None : EPI < 2
Shirley CHCH
(Extreme)
St.TeresaCHCH(None)
23 well-investigated sitesforming 46 case histories: Port Island
Kobe(Extreme)
5 outliers
๐๐% of cases estimated correctly10% of cases with minor inconsistencies
ConclusionsPost-shaking water flow is important, because the primary driving mechanism is upward seepage-induced piping
Severity of sediment ejecta influenced by:โข Drainage contrast (cv profile) โข Excess head (pressure)โข Duration (piping)
Ejecta Potential Index (EPI): 46 case histories (23 sites & 4 earthquakes)90% well-estimated
AcknowledgementsPEER-Transportation Research Program
Prof. Pedro Arduino (UW)Long Chen (UW)Sjoerd van Ballegooy (TT)
NSF Grant CMMI-561932Ministry of Finance of Republic of Indonesia-Indonesia Endowment Fund for Education (LPDP)