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8/8/2011 1
Monitoring Geohazards Impacting Highway Projects
using TDR
Kevin M. O'Connor, Ph.D., P.E.GeoTDR, Inc.
Westerville, Ohio
Geohazards Impacting Transportation in the Appalachian Region
Chattanooga August 2011
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Cables can be grouted into boreholes or trenches to monitor deformation
TDR Cable Tester
Crimp In Cable
Expansive
Cement Grout
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Battery-operated MTDR unit
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Inactive Mine Subsidence
SR 91, Saltville, Virginia
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NEW ALIGNMENT
TDR MONITORINGCABLE
EXISTING SR91
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PLANT AREA
STATE ROUTE 91
NEW ALIGNMENT
Automated, remote
Early Warning
Public safety
Maintain highway access
Limit Liability
Construction Safety
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DAS 1 DAS 2
DAS 3
DAS 4
CO. RD. 745
SR 91Precise Level Monuments
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Total Subsidence SR-91 by Precise Level Survey (1995-2003)
-180.0
-160.0
-140.0
-120.0
-100.0
-80.0
-60.0
-40.0
-20.0
0.0
-20 0 20 40 60 80 100 120 140 160 180 200
Distance (meters)
Vert
ical
mov
emen
t (m
illim
eter
s)
HY-91 HY-91A B11 B10 B9 B8 B-7 B1 B2 B3 FD FC FBFA B4 B5 B67/7/95
6/11/986/14/20006/26/20011/10/2002
7/14/2003
0.06 mm/day
0.03 mm/day
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Cable TDR1
Shearat
10 ft
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0
5
10
15
6/1/2001 7/1/2001 7/31/2001 8/30/2001 9/29/2001 10/29/2001 11/28/2001 12/28/2001 1/27/2002 2/26/2002 3/28/2002
DEF
ORM
ATIO
N. m
m
Precipitation events7/27 and 7/30
Precipitation event 8/27
TDR1 Shear at 10 ft
0.04 mm/day 0.02 mm/day 0.01 mm/day
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Karst Sinkhole Subsidence
I-70 Interchange
Frederick, Maryland
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SITE
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Karst Sinkhole Subsidence
I-70 Interchange
Frederick, Maryland
Automated remote
Extensive area
DoT O&M monitor effectiveness of stabilization
Public safety
Early warning
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subsidence
Long Mine
Abandoned Mine Subsidence
I-70, Muskingum Co., Ohio
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124+00 131+00
131+00 148+00
DAS at 138+00
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Coaxial Multiplexer
ModemTDR Cable Tester
Programmable Data Logger
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EBPA
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
0 500 1000 1500 2000 2500
Distance along cable, ft
Ref
lect
ion
Mag
nitu
de, r
ho
6/16/2010 6/27/2010 6/30/2010
end of cable at 1760 ft
crimps
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-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
0 100 200 300 400 500 600
Ref
lect
ion
Coe
ffici
ent,
rho
Distance, m
EB Passing Lane Trench B
Current Baseline Difference
baseline
current
difference
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Abutment Slope Movement
I-64, Sulphur, Indiana
Forensic
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Fill
Silty Clay LayerSoft Shale
Limestone
TDR Cable
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Fill
Silty Clay
Soft ShaleLimestone
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Typical Costs MTDR unit $3,600 Cable on Spool $1/ft Remote DAS $10,000
INSTALLED CABLE COST Trench $7/ft Vertical hole $15-$25 /ft Angled hole $30-$45 / ft Inside inclinometer casing $3-$5 /ft
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Monitoring Geohazards Impacting Highway Projects
using TDR
Kevin M. O'Connor, Ph.D., P.E.GeoTDR, Inc.
Westerville, Ohio
Geohazards Impacting Transportation in the Appalachian Region
Chattanooga August 2011