i traveled to haiti with my graduate student, melinda
TRANSCRIPT
• I traveled to Haiti with my graduate student, Melinda Jean-Louis (a Haitian native) and Haiti Engineering in July 2013 to perform surface wave testing and present our project to interested parties. We visited Haiti for 10 days and completed seismic testing at 8 sites in Haiti. We used seismic surface wave testing to derive shear wave velocity profiles performed seismic site response analyses with the derived profiles. We calculated design spectral acceleration values and presented them in a report to Haiti Engineering (attached). Haiti Engineering passed this information along to interested parties who will performing reconstruction, including the Catholic Church and the Samuel Dalembert Foundation.
• While in Haiti, I gave a presentation to the Papal Nuncio to Haiti along with other
representatives from the Catholic Church, local engineering firms, and Prof. Christian Rousseau from the University of Haiti on how our methods could be used to improve capabilities for seismic design in Haiti.
• We developed a user’s manual on how to use the field equipment to perform seismic
surface wave testing, analyze the data, and perform seismic site response analysis. We also provided information on how to use the shear wave velocity data derived from surface wave testing for various geotechnical design applications as a replacement to traditional soil borings. Since there are only a few drill rigs in the entire country, the local geoscientists are very interested in being able to use seismic surface wave testing as a replacement to soil borings.
• We sent the equipment to Haiti Engineering along with the User’s Manual (attached) so they can perform the testing themselves.
• The University of Kentucky online daily publication UK Now contained a feature story
on our efforts in Haiti.
• We appeared on the local NBC affiliate WLEX (Channel 18) as part of their “Making a Difference” spot on the 5:00 news. The story aired on November 20, 2013.
• As a result of the experience we acquired in Haiti, we are now in a position to solicit
funds for similar projects in other nations that may result in as much as $14 million in sponsored research. This would not have been possible without the GWB experience in Haiti, which demonstrates that the GWB project will most likely lead to humanitarian engineering efforts around the world.
• The University of Kentucky chapter of Engineers Without Borders is very interested in our work in Haiti and would like to participate in future projects, which is likely.
• Graduate student Melinda Jean-Louis will earn her Master’s degree in May 2014 based
on the work she did on this project.
• We will present the results of our study at the 2014 SEG Annual Meeting and submit them for publication in the SEG peer-reviewed journal Interpretation
September 18, 2013 Mr. Herby G. Lissade, P.E. Haiti Engineering, Inc. 9384 Boulder River Way Elk Grove, CA 95624 RE: Field Seismic Testing and Seismic Site Response Analyses at Selected Sites in Haiti Dear. Mr. Lissade, SUMMARY
Spectral-Analysis-of-Surface-Waves (SASW) testing was performed in July 2013 at selected sites in Haiti to measure the shear wave velocity (vs) profiles. The shear wave velocity information was used to perform seismic site response analyses in accordance with the 2012 International Building Code, which incorporates ASCE Standard 7-10 by reference. This information was used in the General Procedure (ASCE 7-10 Section 11.4) to calculate short-period and long-period design ground surface spectral acceleration values (SDS and SD1) for each site, which can be used to perform seismic design for buildings DERIVATION OF SHEAR WAVE VELOCITY PROFILES The SASW method involves the use of an impulsive seismic energy source and a pair of receivers spaced an equal distance apart in a straight line as shown in Fig. 1. When the ground is impacted, surface waves are generated. As they pass the two receivers, the energy recorded at each receiver is analyzed for spectral content. Differences in phase between the two receivers are calculated at each frequency, and this information is used to calculate variations in surface wave velocity with wavelength, or “dispersion.” Since shorter-wavelength velocities only depend on shallow material and longer-wavelength velocities depend upon deeper material, variations in velocity with wavelength are indicative of variations in shear wave velocity (vs) with depth. By inverting the data using numerical analysis, the vs profile (vs as a function of depth) is derived.
Testing was performed at several sites in Haiti in July 2013. Test locations are summarized in Table 1 and their locations are depicted in Fig. 2. Field data were recorded using a Data Physics Quattro dynamic signal analyzer with 4.5-Hz geophones as receivers. A sledge hammer was used as an impulsive energy source with receiver spacings of 10, 20, and 40 ft. By combining dispersion curves derived using a range of
Seismic Site Response Analysis at Selected Sites in Haiti
Page 1 of 22
receiver spacings, a “composite” dispersion curve is derived. The composite dispersion curve is defined over a broader bandwidth, which helps constrain the inversion process.
The composite dispersion curves derived from field testing were analyzed using the WinSASW forward modeling software package developed at the University of Texas. Forward modeling is performed iteratively by assuming a model vs profile and deriving a theoretical dispersion curve. The model vs profile is refined until an acceptable match between the theoretical dispersion curve and the experimental dispersion curve is achieved. Experimental and theoretical surface wave dispersion curves are shown in Appendix A, and the resulting vs profiles are illustrated in Appendix B. Shear wave velocity profiles derived for each test are also given in Appendix C. APPLICATION OF ASCE 7-10 TO CALCULATE SEISMIC DESIGN PARAMETERS The vs data recorded during SASW testing were used to perform seismic site response analyses according to the General Procedure (ASCE 7-10 Section 11.4). To apply the General Procedure, the average shear wave velocity within the upper 100 ft (
sv ) was calculated using the following equation:
∑
∑=
=
=n
1i si
i
n
1ii
s
vd
dv , (ASCE 7-10 Eqn. 20.4-1)
where di and vsi are the thickness and shear wave velocity in the ith layer of a layered soil/rock profile, and the total thickness of the top n layers is 100 ft. Using the above equation, average shear wave velocities were calculated, and the sites were classified. Seismic site classifications are included in Table 1 for each test point. Application of the General Procedure starts with estimating the Maximum Considered Earthquake (MCE). The MCE has associated peak and spectral acceleration values which have a 2% probability of being exceeded during a 50-year exposure period. Information regarding MCE bedrock shaking for Haiti was published by Frankel et al1. For the sites in Haiti, the short-period (0.2 s) and long-period (1.0 s) spectral acceleration associated with the MCE, SS and S1, are included in Table 1. The MCE parameters SS and S1 represent bedrock spectral acceleration, but they must be corrected to account for the effect of the soil column, which tends to amplify strong ground motion. To make this correction, the site coefficients Fa and Fv are derived based on site class and bedrock spectral acceleration. Short-period and long-period surface spectral acceleration, SMS and SM1, are expressed as:
1Frankel, A., Harmsen, S., Mueller, C., Calais, E., and Haase, J., 2011, “Seismic Hazard Maps for Haiti,” Earthquake Spectra, Vol. 27, No. S1, pp. S23-S41.
Seismic Site Response Analysis at Selected Sites in Haiti
Page 2 of 22
SMS = FaSS (ASCE 7-10 Eqn. 11.4-1) and SM1 = FvS1. (ASCE 7-10 Eqn. 11.4-2) The coefficient Fa is selected using ASCE 7-10 Table 11.4-1, and the coefficient Fv is selected using ASCE 7-10 Table 11.4-2. The spectral acceleration values SMS and SM1 represent spectral acceleration levels at the ground surface corresponding to the MCE. For design purposes, these values are multiplied by 0.667 to derive design ground surface spectral acceleration values SDS and SD1. Values of SDS and SD1 for each location are included in Table 1. Given SDS and SD1, the design response spectrum is calculated according to ASCE 7-05 Section 11.4.5. For periods less than T0=0.2SD1/SDS, spectral acceleration (Sa) is expressed as:
DS0
DSa ST
TS
S 0.40.6 += (ASCE 7-10 Eqn. 11.4-5)
For periods between T0 and TS=SD1/SDS, Sa is equal to SDS. For periods greater than TS, Sa is expressed as: Sa = SD1/T. (ASCE 7-10 Eqn. 11.4-6) The ground surface design response spectra calculated for each site class are depicted in Fig. 3. Regards, Michael E. Kalinski Michael E. Kalinski, Ph.D. Associate Professor Attachments: Tables and Figures
Appendices
Seismic Site Response Analysis at Selected Sites in Haiti
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Table 1. Description of Test Sites in Haiti
Site Date Tested
Profile No.
Latitude (deg. N)
Longitude (deg. W)
SS (g)
S1 (g)
sv (ft/s)
Site Class
SDS (g)
SD1 (g)
Samuel Dalembert Community Center
July 22, 2013
1 19.0619 -71.9844
1.10 0.38
1,890
C 0.73 0.36 2 19.0620 -71.9848 1,877 3 19.0622 -71.9849 1,944 4 19.0623 -71.9842 2,419 5 19.0626 -71.9843 1,753
St. Famine Church July 20, 2013
1 18.4761 -72.6535 1.61 0.75 821 D 1.07 0.75 2 18.4761 -72.6533 885
St. Gerard Church July 20, 2013
1 18.5305 -72.6227 1.30 0.45
2,103 C 0.87 0.40 2 18.5308 -72.6224 2,104 3 18.5308 -72.6226 2,527 B 0.87 0.30
St. Immaculate Church
July 20, 2013 1 18.5485 -72.5761 1.22 0.42 1,159 D 0.82 0.44
St. Michel Church July 18, 2013
1 18.5406 -72.5874 1.26 0.44
1,803 C 0.84 0.40 2 18.5408 -72.5868 1,502
3 18.5410 -72.5873 1,717
Petit Goave School July 23, 2013
1 18.4191 -72.8532 1.61 0.60 2,181 C 1.07 0.52 2 18.4192 -72.8532 2,421 St. Rose de Lima
Church July 16,
2013 2 18.5106 -72.6328 1.43 0.49 937 D 0.95 0.49
Seismic Site Response Analysis at Selected Sites in Haiti
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Figure 1. Experimental configuration for SASW testing.
Seismic Site Response Analysis at Selected Sites in Haiti
Page 5 of 22
Figure 2. Map of Test Locations in Haiti.
19.2
19.0
18.8
18.6
18.4
18.2
Latit
ude
(Deg
rees
Nor
th)
-73.0 -72.8 -72.6 -72.4 -72.2 -72.0 -71.8Longitude (Degrees West)
Petit Goave
St. MichelSt. GerardSt. Rose
St. Famine
Dalembert
St. Immaculate
Seismic Site Response Analysis at Selected Sites in Haiti
Page 6 of 22
Figure 3. Ground Surface Design Response Spectra for Each Site.
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Spe
ctra
l Acc
eler
atio
n (g
)
0.012 3 4 5 6 7 8 9
0.12 3 4 5 6 7 8 9
12 3 4 5 6 7 8 9
10
Period (seconds)
D
D
D D D D D D D DD
D
D
D
DD
D
DD
DD D
DD D D D D D D D
F
F
F
F F F F F F F F F F
F
F
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F
F
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FF F F
F F F
GB
GB
GB GB GB GBGBGB
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GBGB
GB
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GBGBGB
GBGBGBGBGBGBGBGB GB
GC
GC
GC GC GC GCGCGCGCGC
GC
GC
GC
GC
GC
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GC
GC
GCGC
GCGC
GCGCGCGCGCGCGCGC GC
I
I
I I I I I I I I II
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II I I I I I I I
M
M
M M M M M M M M
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M M M M M M M M
P
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P P P P P P P P
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P P P P P P P
R
R
R R R R R R R R R
R
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R
R
R
R
RR
RR
RR
R R R R R R R
D DalembertF St. Famine
GB St. Gerard Site Class BGC St. Gerard Site Class C
I St. ImmaculateM St. MichelP Petit GoaveR St. Rose de Lima
Seismic Site Response Analysis at Selected Sites in Haiti
Page 7 of 22
Appendix A
Experimental and Model Dispersion Curves
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
Dalembert Profile 1
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
Dalembert Profile 2
Seismic Site Response Analysis at Selected Sites in Haiti
Page 8 of 22
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
Dalembert Profile 3
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
Dalembert Profile 4
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
Dalembert Profile 5
Seismic Site Response Analysis at Selected Sites in Haiti
Page 9 of 22
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Famine Profile 1
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Famine Profile 2
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Gerard Profile 1
Seismic Site Response Analysis at Selected Sites in Haiti
Page 10 of 22
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Gerard Profile 2
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Gerard Profile 3
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Immaculate Profile 1
Seismic Site Response Analysis at Selected Sites in Haiti
Page 11 of 22
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Michel Profile 1
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
1002
Wavelength (ft)
Experimental Model
St. Michel Profile 2
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
1002
Wavelength (ft)
Experimental Model
St. Michel Profile 3
Seismic Site Response Analysis at Selected Sites in Haiti
Page 12 of 22
2500
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
1002
Wavelength (ft)
Experimental Model
Petit Goave Profile 1
2500
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
1002
Wavelength (ft)
Experimental Model
Petit Goave Profile 2
2000
1500
1000
500
0
Surfa
ce W
ave
Velo
city
(ft/s
)
12 3 4 5 6 7 8 9
102 3 4 5 6 7 8 9
100
Wavelength (ft)
Experimental Model
St. Rose de Lima Profile 2
Seismic Site Response Analysis at Selected Sites in Haiti
Page 13 of 22
Appendix B Shear Wave Velocity Profile Graphs
100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
Dalembert Profile 1100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
Dalembert Profile 2
100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
Dalembert Profile 3100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
Dalembert Profile 4
Seismic Site Response Analysis at Selected Sites in Haiti
Page 14 of 22
100
80
60
40
20
0D
epth
(ft)
40003000200010000Shear Wave Velocity (ft/s)
Dalembert Profile 5100
80
60
40
20
0
Dep
th (f
t)40003000200010000
Shear Wave Velocity (ft/s)
St. Famine Profile 1
100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
St. Famine Profile 2
100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
St. Gerard Profile 1
Seismic Site Response Analysis at Selected Sites in Haiti
Page 15 of 22
100
80
60
40
20
0D
epth
(ft)
40003000200010000Shear Wave Velocity (ft/s)
St. Gerard Profile 2
100
80
60
40
20
0
Dep
th (f
t)40003000200010000
Shear Wave Velocity (ft/s)
St. Gerard Profile 3
100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
St. Immaculate Profile 1
100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
St. Michel Profile 1
Seismic Site Response Analysis at Selected Sites in Haiti
Page 16 of 22
100
80
60
40
20
0D
epth
(ft)
40003000200010000Shear Wave Velocity (ft/s)
St. Michel Profile 2
100
80
60
40
20
0
Dep
th (f
t)40003000200010000
Shear Wave Velocity (ft/s)
St. Michel Profile 3
100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
Petit Goave Profile 1100
80
60
40
20
0
Dep
th (f
t)
40003000200010000Shear Wave Velocity (ft/s)
Petit Goave Profile 2
Seismic Site Response Analysis at Selected Sites in Haiti
Page 17 of 22
100
80
60
40
20
0D
epth
(ft)
40003000200010000Shear Wave Velocity (ft/s)
St. Rose de Lima Profile 2
Seismic Site Response Analysis at Selected Sites in Haiti
Page 18 of 22
Appendix C Shear Wave Velocity Profile Data
Dalembert Profile 1
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-2.5 350 2.5-7.5 1500
7.5-42.5 1800 42.5-100.0 2500
Dalembert Profile 2
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-5.0 500 5.0-25.0 1300
25.0-65.0 2600 65.0-100.0 2800
Dalembert Profile 3
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-5.0 580 5.0-15.0 1300
15.0-95.0 2400 95.0-100.0 2800
Dalembert Profile 4
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-7.0 500 7.0-27.0 2900
27.0-67.0 3400 67.0-100.0 3800
Seismic Site Response Analysis at Selected Sites in Haiti
Page 19 of 22
Dalembert Profile 5 Depth Interval
(ft) Shear Wave Velocity
(ft/s) 0.0-5.0 500
5.0-25.0 1000 25.0-65.0 2600 65.0-100.0 3000
St. Famine Profile 1
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-15.0 420 15.0-35.0 800 35.0-75.0 900 75.0-100.0 1500
St. Famine Profile 2
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-4.0 320 4.0-12.0 500
12.0-20.0 600 20.0-60.0 900 60.0-100.0 1500
St. Gerard Profile 1
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-3.5 420 3.5-13.5 1200
13.5-100.0 2800
St. Gerard Profile 2 Depth Interval
(ft) Shear Wave Velocity
(ft/s) 0.0-4.2 480
4.2-29.2 1200 29.2-100.0 4000
Seismic Site Response Analysis at Selected Sites in Haiti
Page 20 of 22
St. Gerard Profile 3 Depth Interval
(ft) Shear Wave Velocity
(ft/s) 0.0-6.2 570
6.2-18.2 1500 18.2-100.0 4000
St. Immaculate Profile 1
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-25.0 460 25.0-45.0 2100 45.0-85.0 2400 85.0-100.0 2600
St. Michel Profile 1
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-5.0 520 5.0-25.0 1200
25.0-65.0 2400 65.0-100.0 2800
St. Michel Profile 2
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-6.6 500 6.6-48.6 1200
48.6-100.0 2800
St. Michel Profile 3 Depth Interval
(ft) Shear Wave Velocity
(ft/s) 0.0-8.0 700
8.0-15.0 1150 15.0-45.0 1200 45.0-100.0 3500
Seismic Site Response Analysis at Selected Sites in Haiti
Page 21 of 22
Petit Goave Profile 1 Depth Interval
(ft) Shear Wave Velocity
(ft/s) 0.0-5.0 750
5.0-10.0 1100 10.0-20.0 2000 20.0-100.0 2700
Petit Goave Profile 2
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-4.5 800 4.5-10.5 1100
10.5-22.5 2000 22.5-100.0 3200
St. Rose de Lima Profile 2
Depth Interval (ft)
Shear Wave Velocity (ft/s)
0.0-3.5 450 3.5-13.5 800
13.5-100.0 1000
Seismic Site Response Analysis at Selected Sites in Haiti
Page 22 of 22
TUTORIAL FOR PERFORMING FIELD SASW SEISMIC TESTING TO OBTAIN SHEAR WAVE VELOCITY DATA
Prepared by:
Prof. Michael E. Kalinski, Ph.D., P.E. Melinda Jean-Louis
University of Kentucky Department of Civil Engineering
161 Raymond Bldg. Lexington, KY 40506-0281 Tel: (001) 859-257-6117
Email: [email protected]
October 30, 2013
Table of Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Acquiring Field SASW Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Deriving the Shear Wave Velocity Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4 Deriving the Design Response Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5 Correlating Shear Wave Velocity to Other Geotechnical Parameters . . . . . . . 26 6 Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
Seismic surface wave testing is a nondestructive geophysical method where
surface waves are generated and measured at the ground surface. There are several
methods used in practice today, but the oldest and simplest method is the Spectral-
Analysis-of-Surface-Waves (SASW) method. The SASW method involves the use of an
impulsive seismic energy source and a pair of receivers (geophones) spaced an equal
distance apart in a straight line as shown in Fig. 1. When the ground is impacted,
surface waves are generated. As they pass the two receivers, the energy recorded at
each receiver is analyzed for spectral content. Differences in phase between the two
receivers are calculated at each frequency, and this information is used to calculate
variations in surface wave velocity with wavelength, or “dispersion.” Since shorter-
wavelength velocities only depend on shallow material and longer-wavelength velocities
depend upon deeper material, variations in velocity with wavelength are indicative of
variations in shear wave velocity (vs) with depth. By modeling the data using numerical
analysis, the vs profile (vs as a function of depth) is derived. Modeling is performed
using the WinSASW software, which is described in detail later in this tutorial.
To perform the field test, a dynamic signal analyzer is used. A dynamic signal
analyzer is similar to an oscilloscope with the added feature of real-time spectral
analysis. The system provided to Haiti Engineering includes a Data Physics Quattro
analyzer as depicted in Fig. 2. The Quattro is accompanied by a PC that operates
using the Windows XP platform. The user is encouraged to read the accompanying
Quattro User’s Manual that was provided by Data Physics. Herein, a detailed step-by-
1
step tutorial is provided to allow the field technician to successfully use the Quattro to
acquire SASW data.
Figure 1. Experimental configuration for SASW testing
Figure 2. The Data Physics Quattro Dynamic Signal Analyzer.
2
2. Acquiring Field SASW Data
Step 1: Identify a location to perform field SASW testing. A flat or gently sloping
stretch of land is recommended with at least 120 ft of unobstructed alignment to
accommodate the entire length of the SASW array. Use a GPS to acquire latitude and
longitude data, which will be used later to perform the seismic site response analysis.
Step 2: Power up the PC. Power up the PC that is provided as part of the system. A
450-watt power inverter is also provided. Use the inverter during testing to prevent
power loss during the test.
Step 3: Connect the Quattro to the PC. Use the cable that is included with the
Quattro to connect the Quattro to a USB port on the PC.
Step 4: Launch the Driver Software. Click on the “Start” menu in the bottom left
corner of the PC screen and launch the “Signal Calc 240 Dynamic Signal Analyzer”
software.
Step 5: Select the Appropriate Data Acquisition Configuration for SASW Testing.
Draw down the “Test” menu in the software (Fig. 3). Select “Open” and then select
“newtest.trf” (Fig. 4). This will select the appropriate parameters and display windows
for SASW testing. Once “newtest.trf” is selected, a screen with four windows will
appear (Fig. 5). The four windows, from upper left going clockwise, are:
Window 1: Wrapped phase difference (H1,2). This is the frequency-domain difference in phase between the two receivers in the array in degrees, with one cycle corresponding to 360 degrees. It is also referred to as a transfer function. Window 2: Time-domain record from near receiver (X1). This is voltage plotted as a function of time for the geophone that is located nearest the source location corresponding to Channel 1 on the dynamic signal analyzer.
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Window 3: Time-domain record from the far receiver (X2). This is voltage plotted as a function of time for the geophone that is located farthest from the source location corresponding to Channel 2 on the dynamic signal analyzer. Window 4: Coherence (C1,2). This is a frequency-domain cross-correlation between the two signals observed at the near and far receiver. A coherence value near 1.0 indicates a strong signal.
Figure 3. Opening a Data Acquisition Configuration File.
Figure 4. Selecting “newtest.trf” to perform SASW testing.
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Figure 5. Configuration of Windows for SASW Testing using the Quattro.
Step 6: Deploy the Geophones. Place the geophones on the ground at a distance of
10 ft apart. If the ground is soil, use the spikes. If the ground is hard or paved, replace
the spikes with the heavy brass disks and place them on the ground. In either case, the
geophones should be vertically oriented to optimize data quality. Once the geophones
are deployed, place the rubber pad at a distance from one of the geophones that is
equal to the spacing between the geophones. For the 10-ft geophone spacing, the mat
should be placed 10 ft from the nearest geophone.
Step 7: Connect the Geophones to the Quattro. Connect the geophone nearest the
rubber pad to the “IN 1” BNC connector on the Quattro and connect the other geophone
to the “IN 2” BNC connector.
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Step 8: Select an Appropriate Bandwidth for Acquisition. Data acquisition will be
performed using receiver spacings of 10 ft, 20 ft, and 40 ft. As the receiver spacing
increases, the acquisition bandwidth decreases. For these three spacings, change the
“FSpan” parameter in the upper left corner of the window to 400 Hz, 200 Hz, or 100 Hz,
respectively.
Step 9: Acquire SASW Data in the Forward Direction at a Receiver Spacing of 10
ft. Once you have placed the receivers 10 ft apart and placed the rubber pad 10 ft from
the near receiver, you can begin the test. Click the green “Start” button in the upper left
corner of the screen and have a worker begin repeatedly striking the rubber pad with a
sledge hammer. As the worker does this, you will observe hammer blows in Windows 2
and 3. In Window 1, you will observe the sawtooth pattern of the phase spectra
develop. As the worker continues to strike the pad, the signal adds up while the noise
cancels out, so the phase spectrum gets better and better. Data acquisition is complete
when the Number of Frames in the upper left corner of the screen reaches10 (“Frames:
10), which should take around 18 seconds for a 400-Hz bandwidth (NOTE: it will take
more time when acquiring at shorter bandwidths). Once the acquisition is complete,
click on the red box labeled “End” that appears in the upper left corner of the screen to
save the data.
The saved data will be located in the C:\SignalCalc\240\newtest.trf\ASCII00xxx
folder, where “xxx” is a counter that increases incrementally with every measurement
that you save. In this folder, you will find four files:
1. C1,2sv00000.txt – coherence function; 2. H1,2sv00000.txt – transfer function (phase spectrum); 3. X1sv00000.txt – time record for near receiver; and 4. X2sv00000.txt – time record for far receiver.
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You will use the first two files to derive the experimental dispersion curve in WinSASW.
When completed, the data should resemble the example shown in Fig. 6.
When acquiring data, the maximum time-domain amplitude can be read off of the
y-axis on Window 2 on the right side of the screen. To optimize the quality of the
spectra, the range of the instrument “Range (EU)” should not be more than an order of
magnitude larger than the observed values. For example, in Fig. 6, the maximum
amplitude on Window 2 is around 150 mV. As seen at the bottom of the screen, the
“Range (EU)” is set to 1.000 V for both channels, so it is set appropriately. If the
maximum amplitude in Window 2 is less than 100 mV, then the range should be
reduced to 100 mV.
Figure 6. Typical Data Acquired from SASW Testing in the Forward Direction
Using the Quattro with a 10-ft receiver spacing.
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Step 10: Acquire SASW Data in the Reverse Direction at a Geophone Spacing of
10 ft. Reverse the BNC connectors on the Quattro and move the pad to the other side
of the array so it is 10 ft from the other receiver. Repeat the measurement as described
in Step 9. You will combine this data with data acquired in the forward direction in
WinSASW. The data acquired in the reverse direction will be somewhat similar to the
data acquired in the forward direction (compare Figs. 6 and 7), but will be different due
to noise and slight differences in the response characteristics of the two geophones.
Figure 7. Typical Data Acquired from SASW Testing in the Reverse Direction
Using the Quattro with a 10-ft receiver spacing.
Step 11: Acquire SASW Data in the Forward and Reverse Directions for Receiver
Spacings of 20 ft and 40 ft. Repeat Steps 9 and 10 using receiver spacings of 20 ft
and 40 ft. For each of the three different receiver spacings, make sure that the center of
the array stays at one point as shown in Fig. 8. The data will appear similar to the data
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acquired a the 10-ft receiver spacing, but the bandwidth will be less and the length of
the time records will be longer as shown in Figs. 9 and 10.
10 ft
20 ft
40 ft
Figure 8. Position of receivers (triangles) for the 10-ft, 20-ft, and 40-ft spacings.
Figure 9. Typical Data Acquired from SASW Testing in the Forward Direction Using the Quattro with a 20-ft receiver spacing.
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Figure 10. Typical Data Acquired from SASW Testing in the Forward Direction Using the Quattro with a 20-ft receiver spacing.
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3. Deriving the Shear Wave Velocity Profile
Step 12: Prepare the ASCII files for input into WinSASW. Locate the six folders in
C:\SignalCalc\240\newtest.trf that contain the ASCII data acquired during the SASW
tests for your location. Each folder contains one coherence file “C1,2sv00000.txt” and
one transfer function file “H1,2sv00000.txt”. Delete the first nine lines of each file.
When saving the files, use the following naming convention:
“(C or T)(spg)(F or R).txt”,
where:
C = coherence function; T = transfer function; spg = receiver spacing: F = forward acquisition; and R = reverse acquisition. For example, a file named “C20R.txt” would be a coherence function recorded in the
reverse direction with a receiver spacing of 20 ft. Place all 12 files (3 receiver spacings
x 2 directions x (coherence function + transfer function)) in the same directory along
with a copy of the application “WSASW123.exe,” which can be found on the desktop of
the PC. This application can be copied as many times as necessary (Fig. 11).
Step 13: Read the Field Data into WinSASW. Click on the “WSASW123” icon in the
folder to launch the program. Begin by loading the forward and reverse spectra
corresponding to the 10-ft receiver spacing. Under “File” in the main menu, select
“Open ASCII Files”, which gives the screen shown in Fig. 12. Under “Test Profile(s)”,
select “Forward and Reverse Profiles” to use the data acquired in both directions. Once
all of the files are entered in the appropriate entry, click on “Read Files” to read the data.
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Step 14: Select an Appropriate Receiver Spacing. Select the “Data” option in the
main menu of WinSASW and enter the appropriate receiver spacing (Fig. 13).
Figure 11. Folder Containing Data from a SASW Test along with the WinSASW
Application.
Figure 12. Reading the SASW Data from the 10-ft Receiver Spacing into
WinSASW.
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Figure 13. Selecting the Correct Receiver Spacing in WinSASW.
Step 15: Mask the Phase Spectrum. Select “Procedure” in the main WinSASW menu
and then select “Masking” to generate a window showing the two pairs of overlapping
spectra (Fig. 14). The forward and reverse spectra are shown in blue and pink and the
average spectrum is shown in brown. The average spectrum is used to cancel out
variations in the response between the two geophones. Masking allows the user to edit
and remove noisy portions of the spectrum, which generally occur at the beginning and
end of the spectrum. Ideally, the spectrum should exhibit a sawtooth pattern.
To mask an interval of the spectrum, the low end and high end of the masked
interval must be defined. The low end is defined by clicking the “First” button and
clicking on the phase spectrum at the desired location. The high end is defined by
clicking on the “Second” button and then clicking on the spectrum at the desired
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location. Once the two boundaries are defined, the number of jumps is input. This
represents the estimated number of times the spectrum has jumped from -180 degrees
to 180 degrees by the end of the masked interval. For masked intervals at the low end
of the spectrum (Fig. 15), this number is typically zero. Once the low end, high end, and
number of jumps are input, the mask is saved by clicking on the “New” button.
Figure 14. Unmasked Spectra to be Edited in WinSASW
A second masking interval can be added to remove noisy high-frequency data.
The same approach is used to define this masked interval. Once the masking is
complete, only the unmasked data of high quality (shown in white in Fig. 16) is used to
derive the dispersion curve. To calculate the dispersion curve, click on “Dispersion” in
the Masking window and then click on “Calculate”.
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Step 16: Build the Composite Dispersion Curve. The dispersion curve calculated
using the field data acquired with a10-ft spacing can be viewed by going to the main
WinSASW window, clicking on “Procedure” and then clicking on “Dispersion Curves”.
When you do this, the experimental dispersion curve derived in the previous step will
appear (Fig. 17). The velocity axis should be rescaled to 0-2000 ft/s and the
wavelength axis should be scaled to 1-300 ft. Scaling the axes is achieved by clicking
on “View” and then “Set Attributes” in the Dispersion Curves window.
Figure 15. Spectra with One Masked Interval.
A “composite” dispersion curve consists of data from several different receiver
spacings. Composite dispersion curves are defined over a broader bandwidth, which
helps to constrain the modeling process. To develop a composite dispersion curve, the
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procedure described in Step 15 is repeated using the data from the 20- and 40-ft
receivers spacings. When the dispersion data are calculated, they are automatically
added to the original dispersion curve derived using the data from the 10-ft spacing (Fig.
18). The resulting composite dispersion curve should exhibit a general trend. If some
of the data do not follow the general trend, the number of jumps in the masking may be
adjusted in an interpretive manner until the data from the three different receiver
spacings coincide. Once the composite dispersion curve is complete, it should be
saved in the Dispersion Curves window by selecting “File” then “Save” then
“Experimental”. The experimental dispersion curve file has a .exd extension but can be
opened and viewed in Word or Notepad as an ASCII file.
Figure 16. Spectra with Two Masked Intervals
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Figure 17. Dispersion Curve Derived using One Receiver Spacing.
Figure 18. Composite Dispersion Curve Derived by Combing Dispersion Curves
from Several Different Receiver Spacings.
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Step 17: Forward Modeling of the Experimental Dispersion Curve. Forward
modeling is performed to derive a shear wave velocity profile for the site. To perform
forward modeling, go back to the main WinSASW window and click on “Procedure” and
then “Theoretical Curves” (NOTE: do not close the Dispersion Curves window while
modeling). This opens a window where you can input an initial estimate for the shear
wave velocity profile. The main parameters that you will vary are S-wave velocity and
layer thickness. For the initial estimate, a three-layer profile is used as shown in Fig.
19. Here, a soil site consisting of 35 ft of soil and weathered rock over intact rock is
estimated. Poisson’s ratio of 0.2 is estimated along with unit weights ranging from 120
pcf to 150 pcf. Initial P-wave velocity is calculated by clicking on the “Update” button as
shown in Fig. 20.
Figure 19. Initial Estimate for Shear Wave Velocity Profile Prior to Calculating P-wave
Velocities.
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Figure 20. Initial Estimate for Shear Wave Velocity Profile after Calculating P-wave
Velocities.
After calculating P-wave velocities, click on “SASWFI” to perform the modeling.
Set the parameters as shown in Fig. 21, and click “Run”. After clicking “Run”, the
theoretical dispersion curve appears in the Dispersion Curves window along with the
experimental dispersion curve. If the initial model is correct, then the theoretical and
experimental dispersion curves will match. However, it is more likely that there will be
differences between the two curves (Fig. 22). In this case, return to the Theoretical
Curves window, adjust your model (Fig. 23) and recalculate the theoretical dispersion
curve. Repeat this process iteratively until the theoretical and experimental dispersion
curves match (Fig. 24).
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Figure 21. Parameters for Calculating Model Surface Wave Dispersion Curve.
Figure 22. Theoretical Dispersion Curve (blue circles) Derived using the Initial
Model Estimate (Fig. 20) Along with Experimental Dispersion Curve (black dots).
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Figure 23. Revised Theoretical Model
Figure 24. Original and Revised Theoretical Dispersion Curves Derived from Original and Revised Models (Figs. 20 and 23) along with Experimental Dispersion Curve.
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Once you have identified a theoretical shear wave velocity profile that provides
an acceptable match to the experimental data, save the theoretical profile in the
“Theoretical” window by clicking on “File” and then “Save”. The profile will have a .prf
extension but is an ASCII file that can be viewed in Word or Notepad. The Dispersion
Curves window (Fig. 23) will show the current and previous theoretical dispersion
curves. Save the theoretical dispersion curve by clicking “File” then “Save” then
“Theoretical” in the Dispersion Curves window. The resulting file will have a .thd
extension but will be an ASCII file. All files generated during WinSASW analysis will be
saved in the same directory where the experimental surface wave data reside (Fig. 25).
Figure 25. File Directory Showing additional Files Generated by WinSASW.
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4. Deriving the Design Response Spectrum
The shear wave velocity data derived from SASW testing are used to perform
seismic site response analyses for seismic design according to the General Procedure
(ASCE 7-10 Section 11.4), which is used in the International Building Code. To apply
the General Procedure, the average shear wave velocity within the upper 100 ft ( sv ) is
calculated using the following equation:
∑
∑=
=
=n
1i si
i
n
1ii
s
vd
dv , (ASCE 7-10 Eqn. 20.4-1)
where di and vsi are the thickness and shear wave velocity in the ith layer of a layered
soil/rock profile, and the total thickness of the top n layers is 100 ft. Using the above
equation, average shear wave velocity is calculated and the site is classified according
to Table 1.
Table 1. Definition of Seismic Site Class based on Shear Wave Velocity. Seismic Site Class Site Description sv (ft/s)
A Hard Rock > 5,000 B Rock 2,500 – 5,000 C Very Dense Soil/Soft Rock 1,200 – 2,500 D Stiff Soil 600 – 1,200 E Soft Clay Soil < 600
F Liquefiable Soil/Very High Plasticity
Soil/Organic Soil/ Very Thick Soft Clay
Not applicable; site-specific site response analysis
required
Application of the General Procedure starts with estimating the Maximum
Considered Earthquake (MCE). The MCE has associated peak and spectral
acceleration values which have a 2% probability of being exceeded during a 50-year
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exposure period. Information regarding MCE bedrock shaking for Haiti was published
by Frankel et al1 based on the latitude and longitude. The short-period (0.2 s) and long-
period (1.0 s) spectral acceleration associated with the MCE, SS and S1, can be
obtained by visiting:
https://geohazards.usgs.gov/secure/designmaps/ww/application.php.
The MCE parameters SS and S1 represent bedrock spectral acceleration, but
they must be corrected to account for the effect of the soil column, which tends to
amplify strong ground motion. To make this correction, the site coefficients Fa and Fv
are derived based on site class and bedrock spectral acceleration. Short-period and
long-period surface spectral acceleration, SMS and SM1, are expressed as:
SMS = FaSS (ASCE 7-10 Eqn. 11.4-1)
and
SM1 = FvS1. (ASCE 7-10 Eqn. 11.4-2)
The coefficients Fa and Fv are defined in ASCE 7-10 as described in Tables 2 and 3.
Table 2. Derivation of Fa. Site Class Ss < 0.25 g Ss = 0.5 g Ss = 0.75 g Ss = 1.0 g Ss > 1.25 g
A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F Not applicable; site-specific site response analysis required
The spectral acceleration values SMS and SM1 represent spectral acceleration
levels at the ground surface corresponding to the MCE. For design purposes, these
1Frankel, A., Harmsen, S., Mueller, C., Calais, E., and Haase, J., 2011, “Seismic Hazard Maps for Haiti,” Earthquake Spectra, Vol. 27, No. S1, pp. S23-S41.
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values are multiplied by 0.667 to derive design ground surface spectral acceleration
values SDS and SD1.
Table 3. Derivation of Fv. Site Class S1 < 0.1 g S1 = 0.2 g S1 = 0.3 g S1 = 0.4 g S1 > 0.5 g
A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.7 1.6 1.5 1.4 1.3 D 2.4 2.0 1.8 1.6 1.5 E 3.5 3.2 2.8 2.4 2.4 F Not applicable; site-specific site response analysis required
Given SDS and SD1, the design response spectrum is calculated according to
ASCE 7-10 Section 11.4.5. For periods less than T0=0.2SD1/SDS, spectral acceleration
(Sa) is expressed as:
DS0
DSa ST
TS
S 0.40.6 += (ASCE 7-10 Eqn. 11.4-5)
For periods between T0 and TS=SD1/SDS, Sa is equal to SDS. For periods greater than
TS, Sa is expressed as:
Sa = SD1/T. (ASCE 7-10 Eqn. 11.4-6)
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5. Correlating Shear Wave Velocity to Other Geotechnical Parameters
The International Building Code contains a simple correlation between shear
wave velocity (which can be obtained from SASW testing) and uncorrected SPT blow
count (which must be obtained from drilling) in its seismic site classification (Table 4).
Correlations using SPT blow count have been developed to estimate many important
geotechnical parameters including:
• undrained shear strength in clays (Table 5); • friction angle and relative density in sands (Table 6); • cyclic resistance in sands due to earthquake loading (Fig. 26) and • settlement potential of footings in sand (Fig. 27); and
Seismic SASW testing can be used to derive shear wave velocity information, which
can be used to estimate SPT blow count. The resulting SPT blow count can be used to
estimate the various geotechnical design parameters described above. Therefore,
SASW testing can be used as an alternative to traditional soil borings to greatly reduce
or eliminate the need for drilling while obtaining reliable estimates of the geotechnical
properties at a site.
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Table 4. Correlation between shear wave velocity and uncorrected SPT blow count with respect to seismic site classification.
Seismic Site Class
Shear Wave Velocity (ft/s)
Uncorrected SPT Blow Count (blows/ft)
A > 5,000 n/a B 2,500 – 5,000 n/a C 1,200 – 2,500 > 50 D 600 – 1,200 15 – 50 E < 600 < 15
Table 5. Correlation between SPT Blow Count and Undrained Shear Strength in Clays.
Soil Consistency Uncorrected SPT Blow Count (blows/ft)
Undrained Shear Strength (psf)
Very Soft < 4 < 250 Soft 2 - 4 250-500
Medium 4 - 8 500-1,000 Stiff 8 - 15 1,000-2000
Very Stiff 15 - 30 2,000-4,000 Hard > 30 > 4,000
Table 6. Correlation between SPT Blow Count, Friction Angle, and Relative Density in Sands.
State of Packing
Uncorrected SPT Blow Count (blows/ft)
Relative Density (Percent)
Friction Angle (degrees)
Very Loose < 4 < 20 < 30 Loose 4 – 10 20 – 40 30 – 35
Compact 10 – 30 40 – 60 35 – 40 Dense 30 – 50 60 – 80 40 – 45
Very Dense > 50 > 80 > 45
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Figure 26. Relationship between Cyclic Resistance Ratio and Overburden-
Corrected SPT Blow Count in Sands.
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Figure 27. Procedure for Estimating Settlement in Sands Based on SPT Blow Count.
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6. Support
Support to assist the user in operating this system and performing the analyses
described herein will be provided free of charge at any time by contacting:
Prof. Michael E. Kalinski, Ph.D., P.E. University of Kentucky Department of Civil Engineering 161 Raymond Bldg. Lexington, KY 40506-0281 USA tel: (001) 859-257-6117 mobile: (001) 859-321-3057 email: [email protected]
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