WP1 - nwo.nl
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SOFTTOP Investigating heterogeneous soft top soils for wave propagation, cyclic degradation and liquefaction potential WP1: Development of a Finite element code incorporating a hydro-mechanical, dynamic formulation to model the response of the shallow subsurface during seismic loading Prof. dr. Michael A. Hicks Dr. J. León González A. MSc. Hilmi Bayraktaroglu MSc. Ching-Yu Chao Prof. dr. Cristina Jommi Dr. Mandy Korff Dr. Wout Broere Dr. Bram van den Eijnden 1
Transcript of WP1 - nwo.nl
SOFTTOP
Investigating heterogeneous soft top soils for wave
propagation, cyclic degradation and liquefaction potential
WP1: Development of a Finite element code incorporating a hydro-mechanical,
dynamic formulation to model the response of the shallow subsurface during
seismic loading
Prof. dr. Michael A. Hicks
Dr. J. León González A.
MSc. Hilmi Bayraktaroglu
MSc. Ching-Yu Chao
Prof. dr. Cristina Jommi
Dr. Mandy Korff
Dr. Wout Broere
Dr. Bram van den Eijnden
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Overview
• Brief description of the SOFTOP Work Packages WP2 & WP3
• WP1 FEM formulation
• Benchmarking
• Geotechnical implementation
• Conclusion
• Future work
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Brief description WP2
0
250
500
750
1000
-1000-750-500-2500
q (
kP
a)
p' (kPa)
A semi-micromechanical
constitutive model
Laminated sand
Similar initial states
Same stress path
Modelling monotonic behavior of laminated sands
Cyclic behaviour of laminated sands
!Drained
Undrained
,n i
i
zx
zz
zy
MSc. Hilmi Bayraktaroglu
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Development of earthquake simulator
Prototype of advanced sensors for organic soils
Modelling monotonic behavior of organic soils
Experimental investigation on cyclic behavior of organic soils
MSc. Ching-Yu Chao
Brief description WP3
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WP1 Goals: to study the behaviour at the soil surface considering:
FEM mesh
Hydro-mechanical formulation
Soil
FEM framework
earthquake
water
Small scale Soil properties
distribution
Large scale soil properties
distribution
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FEM formulation
u-p-U formulation
K = matrices
u = soil displacements
p = water pressure
U = water displacement
f = forces
( , , )
( )
( , , )
s
p
f
F u u u f
K F p f
F U U U f
Dynamic formulation using free-field boundaries
Free-Field BC
2D domain
Viscous dampers
fE = maE
aE
Gajo, A., Saetta, A., & Vitaliani, R. (1994). Evaluation of three‐and
two‐field finite element methods for the dynamic response of saturated
soil. International journal for numerical methods in engineering, 37(7),
1231-1247.
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10m
Soil surface
E = 2500 kPa
n = 0.3
Vs = 19.04 m/s
g = 26.5 kN/m3
6m
E = 1000 kPa
Vs = 12.04 m/s
Benchmarking
A
B
E = 3000 kPa
Vs = 20.86 m/s
E = 6000 kPa
Vs = 29.51 m/s
2m
1m C
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Benchmarking
Ref. solution
SimulationSimulation
Simulation Simulation
A B
C B & C
BenchmarkingRef. solution
Ref. solution Ref. solution
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Benchmarking
Simulation
Ref. solution
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Soil distribution of properties
10m
50m
n = 0.3
E = ?
( ) exp( ( ))LN LNE x Z x
( ) Random fieldE x
log normal meanLN
log normalstandard deviationLN
( ) Normal random fieldZ x
LN = 1.0 x 104 kPa
LN = 4.0 x 103 kPa
E
Van Den Eijnden, A. P., & Hicks, M. A. (2017). Efficient subset simulation for evaluating
the modes of improbable slope failure. Computers and Geotechnics, 88, 267-280.
g = 26.5 kN/m3
PDF: Probability Density Function11
Soil property distributions
qH = 20m qV = 2m
q = Scale of fluctuation
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Geotechnical implementation
(m/s
2)
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-35
-25
-15
-5
5
15
25
35
0 1 2 3 4 5 6 7 8 9 10
Acc (
m/s
2)
Time (s)
DeterministicS - 1S - 2S - 3S - 4S - 5S - 6S - 7
Resonance
Computed ground surface acceleration
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Conclusion
• Using the u-p-U formulation dynamic behaviour (such as earthquakes)
can be simulated accurately,
• By using random fields the soil layering distribution can be depicted
properly, and
• Combining both theories (dynamic hydro-mechanical + Random fields)
wide range of surface accelerations can be obtained and water excess
pressure can be computed,
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Future work
• More realistic surface behaviour can be obtained by using better soil
models which include soil dilatancy and degradation during cyclic
shear deformation (WP2 & WP3),
• The random distribution of properties will be implemented considering
several layers of soil (in contrast to the examples presented in this
presentation in which only one layer was considered)
• Liquefaction potential will be analysed.
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