Ground Penetrating Radar : Basic and Applications for Civil Engineering

Ground Penetrating RadarBasic for Civil Engineering

2014. 04. 17

GPR Basic for Master’s Course

Jiyoung RheeEngineer Researcher

What is RADAR?

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RADAR?

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RADAR? No! Laser

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RADAR

Surveillance(Search) Radar (Army/Aiport)http:// www.naval-technology.com

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RADAR

Weather Radar http://www.kma.go.kr/

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RADAR

3 Dimensional Radar(TRMM PR) [Hurricane Sandy, Oct. 28, 2012 at 1725 UTC (1:25 PM EDT)]http://trmm.gsfc.nasa.gov/ 8/45

RADAR

Navigationhttp://www.nauticexpo.com/

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RADAR

• Radio Detecting And Ranging

• An object-detection system

that uses radio waves to

determine the range, altitude,

direction, or speed of objects.

http://en.wikipedia.org/10/45

RADAR

http://en.wikipedia.org/

Principle of a Sonar or Radar Distance Measurement11/45

G P R ?

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Ground

Penetrating

Radar

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Ground Penetrating Radar

• A geophysical method that

uses radar pulses to image the

subsurface.

• This nondestructive method

detects the reflected signals from

subsurface structures. http://en.wikipedia.org/

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• GPR can be used in a variety of

media, including rock, soil, ice,

fresh water, pavements and

structures.

• It can detect objects, changes in

material, and voids and cracks.http://en.wikipedia.org/

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Deterioration

Approach

Thickness

Pavement

Sink hole

Rebar

Tunnel

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Definitions!

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Dielectric Constant• Dielectric Permittivity is the

property that describes the ability of a material to store electric energy by separating opposite polarity charges in space. (units : farads/metre(F/m))

• Relative dielectric permittivity (dielectric constant) is the ratio of the permittivity of a material to that of free space, 8.854×10−12 F/m. (No unit!)

ASTM D 6432 – 11 3.2.918/45

Electrical Conductivity

• The ability of a material to

support an electrical current

(material property that describes the

movement of electrons or ions) due

to an applied electrical field. (units :

Siemens/metre (S/m)).

ASTM D 6432 – 11 3.2.519/45

Electrical Properties

Approximate Electromagnetic Properties of Various Materials

ASTM D 6432 – 11 Table 1 20/45

Survey & Analysis

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Data Acquisition

ASTM D 6432 – 11 Fig 1.

Schematic Diagram of a Ground-Penetrating Radar System22/45

Data Acquisition

• GPR uses high-frequency radio

waves and transmits into the ground.

• When the wave hits a buried object

or a boundary with

different dielectric constants, the

receiving antenna records variations

in the reflected return signal.


Data Acquisition• The depth range of GPR is limited by

the electrical conductivity of the ground, the transmitted center frequency and the radiated power.

• As conductivity increases, the penetration depth decreases.

• Higher frequencies do not penetrate as far as lower frequencies, but give better resolution.


Data Acquisition

ASTM D 6432 – 11 Fig 1.

Schematic Diagram of a Ground-Penetrating Radar System

Soil

Buried Object

Bed Rock

TransmitterAntenna

ReceiverAntenna

Control Unit

DataDisplay

DataStorage

Ground Surface

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Data Acquisition

ASTM D 6432 – 11 Fig 1.


Soil

Buried Object

Bed Rock

TransmitterAntenna

ReceiverAntenna

Control Unit

DataDisplay

DataStorage

Ground Surface

t1

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Data Acquisition

ASTM D 6432 – 11 Fig 1.


Soil

Buried Object

Bed Rock

TransmitterAntenna

ReceiverAntenna

Control Unit

DataDisplay

DataStorage

Ground Surface

Different EM Properties

t1 t2

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Data Acquisition

ASTM D 6432 – 11 Fig 1.


Soil

Buried Object

Bed Rock

TransmitterAntenna

ReceiverAntenna

Control Unit

DataDisplay

DataStorage

Ground Surface

Different EM Properties

t1 t2

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Received Data

ASTM D 6432 – 11 Fig 1.

Soil

Buried Object

Bed Rock

TransmitterAntenna

ReceiverAntenna

Control Unit

DataDisplay

DataStorage

Ground Surface

t1 t2

A1

A2

A Trace

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Data Analysis

• Depth

ASTM D 6432 – 11 Eq. (1)

mVt

d 2

r

m

cV

- c = propagation velocity in free space(3X108m/s)- Vm = propagation velocity through the material- εr = relative permittivity

A Trace

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GPR Survey & Analysis

A Series of Traces

Depth

1 2 3 4 5

Survey

Tim

e

1 2 3 4 5

Survey

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Point Reflector


A Series of Traces

Depth

1 2 3 4 5

Survey

Tim

e

1 2 3 4 5

Survey

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Line Reflector


Wiggle Trace Linescans

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Investigation

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Rebars in a Concrete Pavement

Linescans Wiggle Trace

Surface

Rebars

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Layer Thickness at Bridge Deck

A/C

RebarsBottom

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Subsidence near the Dongtan IC

Patching

Subsidence

B=1.2m

Grouting

Patching

Grouting

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Cultural Treasure in Gyeongju

http://news.dongascience.com/PHP/NewsView.php?kisaid=20120810200002327242

Gyeongju Wolseon, Gyeongsangbuk-do

Seokb

ing

go

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Press News

http://www.yonhapnews.co.kr http://www.e2news.com

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Press News

http://www.joins.com http://www.segye.com

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Now & the Future?

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Now : Research

2012 GPR Conference 42/45

Now : Equipment

2012 GPR Conference

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Now : Software

2012 GPR Conference

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The Future

http://cait.rutgers.edu

The Robot for Bridge Deck Assessment

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Question?

Jiyoung RheeMobile : 031-371-2761

Mailto : [email protected]

http://www.slideshare.net/ssuser6b53da

Ground Penetrating Radar : Basic and Applications for Civil Engineering

Engineering

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