sasw by norinah abd rahman
DESCRIPTION
Site Investigation through Spectral Analysis of Surface Wave Method (SASW) @Kursus Integrasi Web 2.0_ May 2011TRANSCRIPT
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SPECTRAL-ANALYSIS-OF-SURFACE-WAVES (SASW)
METHODS
KH 4653 Site Investigation
1 0 1 5 2 0 2 5 3 0 3 5
L o c a t i o n , m
-25
-20
-15
-10
-5
0
Dep
th, m
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PRE-REQUISITE COURSE
KKKH 2253 Geotechnic I
KKKH 3153 Geotechnic II
**Pre-requisite knowledge -> Physic Form 5**
***KKKH 4223 Geotechnical Engineering Practice***
Kursus Wajib
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OBJECTIVES Explain the importance of site
investigation in engineering practice and SASW technique
Categorize types of site investigation methods available nowadays
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Leaning Tower of Pisa
WHY DO WE NEED TO INVESTIGATE SOIL?
Petronas Twin Towers
Highland Towers
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WHAT ARE WE GOING TO EXPLORE TODAY?
Soil Investigation
TraditionalMethods
Boring
etc
Geophysical Methods
Seismic
Refraction
Reflection
Surface Wave
SASW
MASW
etc
etc
Electrical
etc
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CONTENTSFundamental of Surface Wave Methods
Principles of Surface Wave Methods
Spectral Analysis of Surface Wave(SASW) Technique
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7
Fundamental of Surface Waves
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8Body Waves Surface Waves
Wavelength
· · · ·· · · ·
Compression Wave or Primary Wave (P Wave)
Wavelength
Shear Wave or Secondary Wave (S Wave) Wavelength
Wavelength
air-soil boundary
within soil
Surface Waves and Body Waves
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Propagation of waves
Surface Waves(Rayleigh Waves)
Body Waves(P or S Waves)
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12
3.0
2.5
2.0
1.5
1.0
0.5
0.00.50.40.30.20.10.0
Poisson's Ratio, n
Constrained Compression Wave, VP
Shear Wave, VS
Rayleigh Wave, VR
Nor
mal
ized
Wav
e Ve
loci
ty, V
/VS
0.50.40.30.20.10.0
Constrained
Propagation Velocities of Stress Waves
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Freq=66.48 HzWavelength = 2.0 mVph = 133.0 m/sec
5.0 m
5.0 m
Half-Space
150 m/sec
300 m/sec
700 m/secShear-WaveVelocity
Freq=15.8 HzWavelength = 9.26 mVph = 146.4 m/sec
Freq=11.9 HzWavelength = 17.0 mVph = 202.4 m/sec
Phase-VelocityDispersion Curve
2 m
400
300
200
100
0Phas
e V
eloc
ity, m
/sec
5 6 7 8 91
2 3 4 5 6 7 8 910
2 3 4 5 6 7 8 9100
Wavelength, m
Dispersion Phenomenon of Surface Waves
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16
Principles of Surface Wave Methods
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Analysis Procedure of Surface-Wave Methods
Determination of Phase-Velocity Dispersion Curves
Measurement of Surface Waves[Time or Frequency Domain]
Determination of Shear-Wave Velocity Profile
Inversion Analysis
Iterative Forward Modeling Analysis
SASW Method, CSW Method, MASW Method, ReMi Method, f-k Method, etc.
Measurement ofSurface-Wave Phase Velocities
Determination of 1-D Shear-Wave Velocity (VS) Profile
Construction of 2-D Shear-Wave Velocity ContourUsing a series of1-D VS Profiles
Inversion Analysis
ForwardModeling of Surface-Wave Propagation
A Series of 1-D VS Profiling
(10~20 Profiles)
Analysis Flow of Surface-Wave Measurements
Analysis Procedure of Surface Wave Methods
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18
Surface-Wave Methods
Spectral-Analysis-of-Surface-Waves (SASW) Method
Multichannel Analysis of Surface Waves (MASW) Method
Harmonic Wavelet Analysis of Wave (HWAW) Method
Continuous Surface Wave (CSW) Method
Refraction Microtremor (ReMi) Method
Passive Method
f-k Spectrum Method
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Spectral Analysis of Surface Wave(SASW)
Technique
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20
Setup for SASW Measurements
DR
Dynamic Signal Analyzerwith anti-aliasing filter Frequency Span: 25~52000 Hz Real-time FFT 2 to 4 input channels
Geophones4.5 Hz (for D=0.5~1m)1.0 Hz (for D ≥ 2m)Shielded Cables
Impact SourceAssorted Hammers 100-kg Drop WeightBulldozer
Inter-Receiver Spacings0.5, 1.0, 2.0, 4.0, 8.0 m (for Hammers)16.0, 32.0 m (for 100-kg Drop Weight)64.0, 128.0 m (for Bulldozer)
Source-Receiver DistanceR=D (Conventional SASW)R=1, 2, 4, 8, and 16 D (for CAP-SASW)
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FFT Analyzer Seismic Sources
Geophones
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22
Principles of Phase-Velocity Measurement
360sec 01504.0t
Frequency = 66.48 HzPeriod = 0.01504 sec
phase difference:travel time:
ft
2
Relationship between and t :
2 m
m/sec 0.13301504.0
0.2
tDvphPhase Velocity:
fDvph
2
Receiver 1
Receiver 2
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Surface-Wave Methods
Receiver 1
3
2
1
0Spe
ctra
l Am
plitu
de
8006004002000
Frequency, Hz
D D
2000
1000
0
Unw
rapp
ed P
hase
, deg
8006004002000Frequency, Hz
Spe
ctra
l Am
plitu
de 3
2
1
0 8006004002000Frequency, Hz
FFT
Phase Difference :2 – 1
600
400
200
0
Pha
se V
el.,
m/s
ec
1 10 100Wavelength, m
ExperimentalDispersion Curve
Receiver 2
FFT
-150-100-50
050
100150
Pha
se A
ngle
, deg
8006004002000Frequency, Hz
Phase Unwrapping
(a)
(b)
(c)
Impact, Swept Sinusoidal Vibration, orRandom Noise
D=1m
Receiver 1
3
2
1
0Spe
ctra
l Am
plitu
de
8006004002000
Frequency, Hz
D D
2000
1000
0
Unw
rapp
ed P
hase
, deg
8006004002000Frequency, Hz
Spe
ctra
l Am
plitu
de 3
2
1
0 8006004002000Frequency, Hz
3
2
1
0 8006004002000Frequency, Hz
FFT
Phase Difference :2 – 1
Phase Difference :2 – 1
600
400
200
0
Pha
se V
el.,
m/s
ec
1 10 100Wavelength, m
ExperimentalDispersion Curve
Receiver 2
FFT
-150-100-50
050
100150
Pha
se A
ngle
, deg
8006004002000Frequency, Hz
Phase Unwrapping
(a)
(b)
(c)
Impact, Swept Sinusoidal Vibration, orRandom Noise
D=1m
SASW Method
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-150
-100
-50
0
50
100
150
Pha
se A
ngle
, deg
8006004002000
Frequency, Hz
-150
-100
-50
0
50
100
150
Pha
se A
ngle
, deg
4003002001000
Frequency, Hz
-150
-100
-50
0
50
100
150
Pha
se A
ngle
, deg
200150100500
Frequency, Hz
-150
-100
-50
0
50
100
150
Pha
se A
ngle
, deg
100806040200
Frequency, Hz
-150
-100
-50
0
50
100
150
Pha
se A
ngle
, deg
50403020100
Frequency, Hz
-150
-100
-50
0
50
100
150
Pha
se A
ngle
, deg
2520151050
Frequency, Hz
800
600
400
200
0
Pha
se V
eloc
ity, m
/sec
3 4 5 6 7
12 3 4 5 6 7
102 3 4 5 6 7
1002 3
Wavelength, m
D = 1m
D = 2m
D = 4m
D = 8m
D = 16m
D = 32m
25
20
15
10
5
0
Dep
th, m
8006004002000Shear Wave Velocity, m/sec
InversionAnalysis
CompositeExperimental Dispersion Curve
Inversion Analysis in the SASW Method
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WinSASW, Dedicated Software for the SASW Method
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D=3 m
1 2
S=3, 6, 12, 24, and 48 m
ReceiversNear SourceFar Source
40
30
20
10
0
Dep
th, m
25000Vs., m/sec
0
5
10
15500 5 10 15 20 25 30 35 40 45
Location, m
Dep
th, m
55
Evaluation of 2-D Shear-Wave Velocity Profiles
(100kg) (5kg)
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WHICH ONE?
Traditional Geophysical
Drill a hole Reliable – sample Result refer to one
point only Expensive Can be performed
by labor with supervision
Non-destructive No soil sample Cover large area Cheaper Relatively Fast Expertise needed
throughout the test
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CONCLUSION Today lecture
Importance of site investigationSite investigation categories SASW method
Next lectureRecent Development in SASW MethodSome Applications of SASW in Practice
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THANK YOU!
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