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
PRE-REQUISITE COURSE
KKKH 2253 Geotechnic I
KKKH 3153 Geotechnic II
**Pre-requisite knowledge -> Physic Form 5**
***KKKH 4223 Geotechnical Engineering Practice***
Kursus Wajib
OBJECTIVES Explain the importance of site
investigation in engineering practice and SASW technique
Categorize types of site investigation methods available nowadays
Leaning Tower of Pisa
WHY DO WE NEED TO INVESTIGATE SOIL?
Petronas Twin Towers
Highland Towers
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
CONTENTSFundamental of Surface Wave Methods
Principles of Surface Wave Methods
Spectral Analysis of Surface Wave(SASW) Technique
7
Fundamental of Surface Waves
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
9
Propagation of waves
Surface Waves(Rayleigh Waves)
Body Waves(P or S Waves)
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
13
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
16
Principles of Surface Wave Methods
17
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
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
19
Spectral Analysis of Surface Wave(SASW)
Technique
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)
21
FFT Analyzer Seismic Sources
Geophones
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
23
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
24
-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
25
WinSASW, Dedicated Software for the SASW Method
26
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)
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
CONCLUSION Today lecture
Importance of site investigationSite investigation categories SASW method
Next lectureRecent Development in SASW MethodSome Applications of SASW in Practice
THANK YOU!
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