Ir. Anuar Kasa (UKM)

Seminar Teknikal Kebangsaan Gempa Bumi
Dan Tsunami Di Malaysia
NaTSET 2010
1010-11 November 2010
Study on the Effect of Earthquake on
Retaining Structures
Anuar Kasa and Noor Hasnida Baharudin
Universiti Kebangsaan Malaysia
Pengenalan
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Dari kajian yang dilakukan terhadap kesan gempa bumi yang berlaku di Kobe,
Jepun kebanyakan struktur penahan yang mengalami keruntuhan terdiri dari
tembok jenis konvensional.
Tembok penahan bertetulangkan geosintetik didapati tidak mengalami kegagalan
yang kritikal. Kebanyakannya tidak runtuh (collapse) tetapi berubah posisi secara
mendatar.
Secara umumnya struktur tersebut masih boleh diguna pakai seperti biasa
selepas sedikit pembaikan.
Salah satu faktor penyebab utama ialah penggunaan geosintetik sebagai tetulang
yang boleh menampung ubah bentuk yang besar (large deformation).
Sehingga kini kajian yang terperinci belum dilakukan di Malaysia terutama sekali
melibatkan tanah baki yang berjelekit (Malaysian residual soil) sebagai bahan
timbus.
Objektif Penyelidikan:
• Melihat kesesuaian tanah baki sebagai bahan timbus bagi tembok
penahan bersegmen
• Memantau prestasi tembok penahan bertetulangkan geosintetik
berskala penuh
• Menghasilkan permodelan komputeran untuk menganggar tegasan
dan terikan bagi kes beban statik dan dinamik (seismik)
• Membangunkan sistem pintar yang dapat menganggar kestabilan
dalaman, luaran dan lokal bagi kes beban statik dan dinamik
(seismik)
Metodologi Penyelidikan:
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Data mengenai geosintetik dan tanah baki yang diperolehi dari ujian
makmal digunakan untuk merekabentuk tembok penahan bertetulangkan
geosintetik secara manual
Tembok penahan berskala penuh dibina dan dipasang dengan peralatan
yang sesuai seperti meter condong, tolok keterikan, paip tegak dan meter
tekanan untuk memantau prestasi sebenar tembok tersebut bagi kes beban
statik dan dinamik
Data yang diperolehi dari hasil pemantauan berkala akan dibandingkan
dengan hasil pengiraan berangka kaedah unsur terhingga (FEM) dengan
menggunakan model tanah yang sesuai
Dengan menggunakan kaedah statistik, artificial neural networks (ANN) dan
Adaptive Neuro-Fuzzy Inference System (ANFIS), satu sistem pintar akan
dibangunkan untuk menganggar kestabilan dalaman, luaran dan lokal bagi
tembok penahan tersebut
Pisa II block
200 mm
150
mm
Mechanical
Interlock
Miragrid
geogrid
Broken
faces
305 mm
Machine Direction Strand
Aperture
Node
Cross Machine Direction Strand
DESIGN OF
REINFORCED
SEGMENTAL
RETAINING WALL
"Design Manual for
Segmental Retaining
Walls, Second
Edition", NCMA
“Segmental
Retaining Walls –
Seismic Design
Manual, First
Edition”, NCMA
NCMA DESIGN - MAIN MODES OF FAILURE
NCMA DESIGN - MAIN MODES OF FAILURE
C. LOCAL STABILITY
NCMA DESIGN - EARTH
PRESSURE
DISTRUBUTION AND
FORCE RESOLUTION
DESIGN ASSUMPTIONS
1. Surcharge loads applied at the top of the wall are uniform and transient.
2. Surface and subsurface drainage is provided to prevent the development of
hydrostatic pressures at the back of the wall facia and the reinforced soil zone.
3. Effective stress parameters are used for the internal friction angles of the wall infill,
retained and foundation soils. The ground water table is assumed to be well below the
reinforced zone.
4. Soil unit weights are moist unit weights that include the weight of water in the soil.
5. The long term design strength of the geogrid reinforcement has been established
using appropriate factors of safety for creep reduction, construction damage, biological
and chemical degradation.
6. Seismic loading is not considered.
7. Global stability has been evaluated and found to be acceptable by a qualified
geotechnical engineer.
8. Foundation settlement has been evaluated and found to be acceptable by a
qualified geotechnical engineer.
NCMA DESIGN
METHODOLOGY
FLOW CHART FOR
SRW
Analisa Tanah Baki & Geosintetik
Tensile strength - strain
until failure
40.00
Particle Size Distribution
35.00
Tensile Force (kN/m)
Percent Finer (%)
Wet Sieve Method
100
90
80
70
60
50
40
30
20
10
0
0.01
30.00
25.00
15.00
Diameter (mm)
10
10 % strain
10.00
0.00
0.00
1
Max. strain
gauge
reading: 20
kN/m
20.00
5.00
0.1
Max. Tensile
load: 36.15
kN/m
5 % strain for w all adjacent
to sensitive structure
5.00
10.00
15.00
100
Strain (%)
20.00
25.00
30.00
Analisa Kekuatan Tarik-Keluar (pullout)
Pullout stress vs Displacement
0.050
140 kpa
Pullout stress (N/m m )
0.045
0.040
120 kpa
0.035
0 kpa
100 kpa
0.030
40 kpa
80 kpa
0.025
60 kpa
60 kpa
0.020
80 kpa
40 kpa
0.015
100 kpa
0 kpa
0.010
120 kpa
0.005
140 kpa
0.000
0
20
40
Displacem ent (m m )
Tendency for
Grid Movement
Soil Particles
Tensile Force
Applied
Tf
Miragrid
Passive Soil Resistance
Mobilized by Grid Movement
Soil Shear Resistance
Mobilized by Grid Movement
60
80
Ujian Mengunakan “Shake Table” – sedang maju
CROSS -SECTIONAL VIEW
Pisa II block
Vertical Height
Surcharge = 5 kN/m
Top @ 4.88m
N9 @ 4.35m
N8 @ 3.75m
Miragrid
geogrid
N7 @ 3.15m
N6 @ 2.55m
N5 @ 1.95m
N4 @ 1.35m
Natural slope
Free draining material
(granular soil)
N3 @ 0.9m
N2 @ 0.45m
N1 @ 0.3m
Angle of Wall = 82.9 degree
Foundation
3.40 m
17
FIELD INSTRUMENTATION
Vertical Height
Top @ 4.88m
Reference
M1
I1
M2
PP1
8A
N8 @ 3.75m
M3
Strain gauge (10 units)
Horizontal pressure cell (HP)
8B
8C
Vertical pressure cell (VP)
Inclinometer (I)
Standpipe piezometer (SP)
6A
6B
6C
N6 @ 2.55m
Pnuematic piezometer (PP)
Surface settlement marker (M)
4A 4B
N4 @ 1.35m
4C
4D
HP1
Bottom @ 0.00m
VP1
SP1
3.40 m
Location of Various Type of Instrumentation
18
STRAIN GAUGES
To measure tensile forces along the length of geogrid at different elevation
19
20
FINITE ELEMENT ANALYSIS
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Material Model: Mohr Coulomb
Unit Weight: 20 kN/m3
Young Modulus: 20 Mpa
Poisson’s Ratio: 0.3
Cohesion: 10 kPa
Friction Angle: 30o
Interface Strength Reduction Factor: 0.85
Existing Soil
Total Fixity
Foundation Soil
Horizontal
Fixity
Boundary Conditions of the Model (existing profile)
21
FINITE ELEMENT ANALYSIS
Geogrid
Interfaces
Backfill
Segmental
Blocks
Existing Soil
6.0 m
6.0
m
3.5 m
4.9
m
11.5 m
Foundation Soil
22
FINITE ELEMENT ANALYSIS
23
0 mm
10 mm
20 mm
COMPARISON:
CALCULATED AND MEASURED VALUES
(11 mm)
+ 4.9 m
FEM vertical surface
displacements
7.69 mm
measured
vertical
displacement
20
mm
(N8)
9.24 mm
[17 mm]
(N4)
5.98 mm
measured
horizontal
displacement
(5 mm)
INCLINOMETER
(1 mm)
+ 0.3 m
10 mm
(N6)
(11 mm)
[15 mm]
(9 mm)
FEM
horizontal
displacements
0 mm
[16 mm]
(13 mm)
[13 mm]
SURFACE
+ 0.0 m
24
+ 4.9 m
FEM axial force
distribution
1.39 kN/m (peak)
(0.38)
4 kN/m
2 kN/m
(-0.10)
(-0.07)
0 kN/m
N8
4 kN/m
axial force derived
from strain gauge
2.61 kN/m (peak)
Tensile strength - strain
until fa ilure
2 kN/m
40.00
N6
(* fault)
(3.24)
0 kN/m
(0.09)
2.21 kN/m (peak)
(1.64)
(0.26)
(1.36)
4 kN/m
2 kN/m
(0.18)
0 kN/m
N4
Tensile Force (kN/m)
35.00
Max. Tensile
load: 36.15
kN/m
30.00
25.00
Max. strain
gauge
reading: 20
kN/m
20.00
15.00
10 % strain
10.00
5.00
0.00
0.00
5 % strain f or w all adjacent
to sens itive structure
5.00
10.00
15.00
20.00
25.00
30.00
Stra in (%)
+ 0.3 m
+ 0.0 m
Distributions of axial forces along the geogrid reinforcements
25
Hybrid
Models
Results of Statistical Analyses
RESPONSE SURFACE METHODOLOGY
Linear Model
Pure Quadratic
Model
Interactions
Model
Full Quadratic
Model
Backslope angle
FOS
Surcharge load
Height of wall
RESPONSE SURFACE METHODOLOGY
Linear Model
y = β 0 + β1 x1 + β 2 x2 + β 3 x3
Pure Quadratic Model
y = FOS
x1 = backslope
x2 = load
x3 = height
y = β 0 + β1 x1 + β 2 x2 + β 3 x3 + β11 x12 + β 22 x22 + β 33 x32
Interactions Model
y = β 0 + β1 x1 + β 2 x2 + β 3 x3 + β12 x1 x2 + β13 x1 x3 + β 23 x2 x3
Full Quadratic Model
y = β0 + β1x1 + β2 x2 + β3 x3 + β12x1x2 + β13x1x3 + β23x2 x3 + β11x12 + β22x22 + β33x32
External Stability: FOS against Base Sliding
6
target
linear
5.5
FOS against Base Sliding
5
4.5
4
3.5
3
2.5
2
1.5
1
0
50
100
150
200
250
Order
6
target
pure quadratic
5.5
FOSagainst BaseSliding
5
4.5
4
3.5
3
2.5
2
1.5
1
0
50
100
150
Order
200
250
External Stability: FOS against Base Sliding – cont.
5
target
interactions
4.5
FOSagainst BaseSliding
4
3.5
3
2.5
2
1.5
1
0
50
100
150
200
250
Order
5
target
full quadratic
4.5
FOS against Base Sliding
4
3.5
3
2.5
2
1.5
1
0
50
100
150
Order
200
250
Results of Analyses Using ANN
(Artificial Neural Network)
External Stability: FOS against Base Sliding
5
target
ANN
FOS against Base Sliding
4.5
4
3.5
3
2.5
2
1.5
1
0
50
100
150
200
250
150
200
250
Order
1
0.8
0.6
Error
0.4
0.2
0
-0.2
-0.4
0
50
100
Order
Internal Stability: FOS against Tensile Overstress
9
target
ANN
F O S a g a in s t T e n s ile O v e rs tre s s
8
7
6
5
4
3
2
1
0
0
50
100
150
200
250
150
200
250
Order
1.5
1
0.5
Error
0
-0.5
-1
-1.5
-2
0
50
100
Order
Local Stability: FOS against Connection Failures
5.5
target
ANN
FOS against Connection Failures
5
4.5
4
3.5
3
2.5
2
1.5
1
0
50
100
150
200
250
Order
0.8
0.6
0.4
Error
0.2
0
-0.2
-0.4
-0.6
-0.8
0
50
100
150
Order
200
250
Results of ANFIS
(Adaptive Neuro-Fuzzy Inference System)
Advantages of the Sugeno Method
*
*
*
*
*
It is computationally efficient.
It works well with linear techniques.
It works well with optimization and adaptive techniques.
It has guaranteed continuity of the output surface.
It is well suited to mathematical analysis.
External Stability: FOS against Base Sliding
External Stability: FOS against Overturning
External Stability:
FOS against Bearing Capacity
Internal Stability: FOS against Pullout
Internal Stability: FOS against Tensile Overstress
Internal Stability: FOS against Sliding
Local Stability: FOS against Connection Failures
Local Stability: FOS against Bulging
Number of Geogrid Reinforcement
Length of Geogrid Reinforcement
CONCLUSION
At this stage of research, it can be conluded that
that::
• The instrumented wall has performed satisfactorily
satisfactorily::
Post
Post--construction movements were small
Rate of movement was negligible
Tensile forces were within the permissible limit
Drainage system was also working properly
• Results of FEM analysis agree well with the measured values in
terms of deformations and geogrid forces
• ANFIS could predict the stability of segmental retaining wall very
accurately..
accurately
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Thank you.