ground penetrating radar for utilities mapping and detection ์ warawutti lohawijarn
TRANSCRIPT
Ground Ground Penetrating Penetrating
RadarRadarfor for
Utilities mapping Utilities mapping and Detectionand Detection ์์
Warawutti Loh Warawutti Lohawijarnawijarn
ObjectiveObjective• To determine locations
of buried utilities and a rchaeological structure
s at some underground train stations in Krung
Rattanakosin area
Map of Bangkok with study area
STUDY AREA
Ground Ground Penetrating Radar Penetrating Radar
(GPR)(GPR)•nondestructive method
•gives continuous pictures of underground features /structures without drilling
Applications of Applications of GPRGPR
(http://www.malags.se/ramac/applications.shtml)
• Utilities location• UST detection• Bedrock mapping• Bathymetry
studies• Archeological
investigation• Forensics• Road bed
investigations
• Concrete/Asphalt thickness
• Hydrological investigations
• Fracture mapping• Karst and void detection• Hazardous waste
detection• Landfill delineation• Earth dam studies• sedimentological
studies
Principle of GPRPrinciple of GPR• Transmitter (Tx)
transmits electromagnetic pulses into the ground
• Scattering of signals from buried objects or interfaces
• Scattering signals r eceived and record
ed by receiver (Rx)
Pulse signal of Pulse signal of GPRGPR• (a) pulse signal
of GPR• (b) ideal pulse of
GPR• (c) power
spectrum of pulse (b)
• central frequency
GPR surveyGPR survey• GPR antennae are
moved in a profile• spacing between mea
suring points is given ( spacing between trace
s)• pictures of ground int
erfaces and buried obj ects showed up by alig
nments of trace signa ls on computer monito
r
radargramradargram• Reflection point
appears as hyperbola
• reflection planes appear as planes
• horizontal and vertical resolutions are about 0.01-0.20 m depended on antenna frequency and depth of investigation
GPRGPR•Antennae•Receiver
unit •Transmitte
r unit•Control
Unit•Notebook
computer
Speed of radar p Speed of radar pulsesulsesMedium Relative Permittiv
ityVelocity
(x106 m/s)
Air 1 300Fresh water
81 33
Concrete
4-10 95-150
Asphalt 2 212Clay 4-6 74-150Silt 9-23 63-100
Sand 4-30 55-150
Depth penetration and Depth penetration and Resolution of GPRResolution of GPR
(Parasnis, 1997)(Parasnis, 1997)•Penetration depth ( )
•Vertical resolution : smallest layer thickness detectable is
•Lateral resolution : shape of reflector accurately mapped if its lateral extent greater than a, but diffraction pattern will dominate if its extent less than a
2/11222
2/1
2
1
f2/v
ft
a2v
GPR test line / GPR test line / drainage pipes drainage pipes
GPR tested GPR tested line / electric line / electric
cablecable
GPR tested line GPR tested line /water pipe (iron)/water pipe (iron)
GPR tested line / GPR tested line / water pipe (rubber)water pipe (rubber)
GPR surveyGPR survey
station
Number of lines
Length (meters)
planned
surveyed
planned
surveyed
1( ) Phan Fa 15 16 225 298.5(2) Royal
Palace 13 13 204 184.6
(3) Wang Buraaa 21 21 337 319.4
total 49 50 766 802.5
Phan Fa station Phan Fa station
EquipmentEquipment•Model : 21-0010•S/N : 96 50 01•Antenna : 200
MHz•Sampling
frequency : 2049 MHz
•Recording window : 249.86 ns
•Stacking : 64
AcquisitionsAcquisitions•Antenna separation : 0.6 m
•Survey line spacing : 15 m
•Tracing spacing : 0.10 m
LevelingLeveling
Data ProcessingData Processing• GRADIX v. 1.11• Butterworth
Band Pass Filter : 100-400 MHz with slope of 24 dB
• Elevation statics
• Depth conversion with constant velocity of 10
0m/s
0 .0 4 .0 8 .0 1 2 .0 1 6 .0 2 0 .0D ista n ce a lo n g su rv ey lin e (m )
1
3
5
7
9
1 1
1 3
1 5
Surv
ey lin
e num
ber
Su
rvey
lin
e
nu
mb
er
Survey results at Pha Survey results at Pha n Fa station n Fa station
ภาพสั�ญญาณภาพสั�ญญาณ
23
2018167513119
3
222119171514121086
4
21
Electric
Cable
Water
Pipe
Telephone
Cable
Drainage
Pipe
Water
Pipe
W T WD
Unknown
anomaly
BH18
BH17
Drainage
Pipe
D E
Radargram on line 12, Prasumen Road, Bangkok
0.00-0.20m.: Asphalt
0.20-0.60m.: Road suc-beded, limestone fragments
0.60-4.00m.: SILTY CLAY,brownish grey, medium softto soft.
Bottom of Hole 4.00m.
0.0
1.0
2.0
3.0
4.0
5.0
BORING NO. : BH-18
0.00-0.50m.: Refilled sand
0.50-1.50m.: Stiff CLAY withbrick Fragments
1.50-3.50m.: Ancient wall,trace of soft clay at 1.70-1.80m and 3.20-3.30m.
3.50-4.00m.: SANDY CLAY,grey to dark grey, softBottom of Hole 4.00m.
0.0
1.0
2.0
3.0
4.0
5.0
BORING NO. : BH-17
Boring Logs on line 12, Prasumen Road, Bangkok
Boring No.17Boring No.18
ConclusionsConclusions•Present locations of buried utilities were picked up
•Radar reflections from unknown causative bodies were later identified by drilling as parts of ancient walls
AcknowledgemeAcknowledgementnt
• Geotechnical & Foundation Engineeri ng Co., Ltd.
• Mr Somchai Payongpan and GFE team• Department of Physics, Faculty of Sci
ence, Prince of Songkla University•International Programme in the Physical Sciences (IPPS), Uppsala University, Sweden