1. Ground Penetrating Radar for Utilities mapping and Detection ์
Warawutti Lohawijarn

2. Objective
To determine locations of buried utilities and archaeological structures at some underground train stations in Krung Rattanakosin area

3. Map of Bangkok with study area

4. Ground Penetrating Radar (GPR)
nondestructive method
gives continuous pictures of underground features /structures without drilling

5. Applications of GPR (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

6. Principle of GPR
Transmitter (Tx) transmits electromagnetic pulses into the ground
Scattering of signals from buried objects or interfaces
Scattering signals received and recorded by receiver (Rx)

7. Pulse signal of GPR (a) pulse signal of GPR (b) ideal pulse of GPR
(c) power spectrum of pulse (b)
central frequency

8. GPR survey GPR antennae are moved in a profile
spacing between measuring points is given (spacing between traces)
pictures of ground interfaces and buried objects showed up by alignments of trace signals on computer monitor

9. radargram Reflection point appears as hyperbola
reflection planes appear as planes
horizontal and vertical resolutions are about m depended on antenna frequency and depth of investigation

10. GPR Antennae Receiver unit Transmitter unit Control Unit
Notebook computer

11. Relative Permittivity
Speed of radar pulses
Medium
Relative Permittivity
Velocity (x106 m/s)
Air 1
300
Fresh water 81 33
Concrete
4-10
95-150
Asphalt 2
212
Clay
4-6
74-150
Silt
9-23
63-100
Sand
4-30
55-150

12. Depth penetration and Resolution of GPR (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

13. GPR test line / drainage pipes

14. GPR tested line / electric cable

15. GPR tested line /water pipe (iron)

16. GPR tested line / water pipe (rubber)

17. GPR survey station Number of lines Length (meters) planned surveyed 15
(1) Phan Fa 15 16
225
298.5
(2) Royal Palace 13
204
184.6
(3) Wang Burapa 21
337
319.4
total 49 50
766
802.5

18. Phan Fa station

19. Equipment Model : 21-0010 S/N : 96 50 01 Antenna : 200 MHz
Sampling frequency : 2049 MHz
Recording window : ns
Stacking : 64

20. Acquisitions Antenna separation : 0.6 m Survey line spacing : 15 m
Tracing spacing : 0.10 m

21. Leveling

22. Data Processing GRADIX v. 1.11
Butterworth Band Pass Filter : MHz with slope of 24 dB
Elevation statics
Depth conversion with constant velocity of 100 m/s

23. Survey results at Phan Fa station23 20 18 16 7 5 13 11 9 3 22 21 19 17 15 14 12 10 8 6 4 2 1
ภาพสัญญาณ
Survey line number

24. Radargram on line 12, Prasumen Road, Bangkok
Electric Cable
Water Pipe
Telephone Cable
Drainage Pipe W T D
Unknown anomaly
BH18
BH17 E

25. Boring Logs on line 12, Prasumen Road, Bangkok
Boring No.17
Boring No.18

26. Conclusions Present locations of buried utilities were picked up
Radar reflections from unknown causative bodies were later identified by drilling as parts of ancient walls

27. Acknowledgement Geotechnical & Foundation Engineering Co., Ltd.
Mr Somchai Payongpan and GFE team
Department of Physics, Faculty of Science, Prince of Songkla University
International Programme in the Physical Sciences (IPPS), Uppsala University, Sweden