ground penetrating radar (gpr) for pavement … · infrasense, inc. ground penetrating radar (gpr)...
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INFRASENSE, Inc.INFRASENSE, Inc.
Ground Penetrating Radar
(GPR) for Pavement
Condition Evaluation
by
Kenneth Maser
Infrasense, Inc.
Pavement Evaluation 2010
Roanoke, VA
INFRASENSE, Inc.INFRASENSE, Inc.
Presentation Outline
• Background
• GPR Equipment and Software
• Pavement Applications
• Future Prospects
INFRASENSE, Inc.INFRASENSE, Inc.
What is GPR?
• Transmits pulsed radio waves through
pavement materials
• Waves reflect at material boundaries
• Arrival time and strength of reflections
determine material depths, thicknesses, and
properties
INFRASENSE, Inc.INFRASENSE, Inc.
What does GPR Detect?
• Thickness of pavement layers
• Reinforcing steel
• Density variations
• Subsurface moisture
• Voids
INFRASENSE, Inc.INFRASENSE, Inc.
Evolution of GPR
• 1960’s,70’s - early development
– Military applications
– Tunnel and mine detection
• 1980’s - Initial adaptation to highways
• 1990’s - Practical development and
implementation for pavements
• 2000+ - Adaptation by highway agencies
INFRASENSE, Inc.INFRASENSE, Inc.
GPR Equipment
• Data acquisition and control systems
• GPR antennas
– Air Coupled
– Ground Coupled
INFRASENSE, Inc.INFRASENSE, Inc.
1 GHz Horn Antennas
INFRASENSE, Inc.INFRASENSE, Inc.
Current Horn Antennas
1 GHz Horns 2 GHz Horns
INFRASENSE, Inc.INFRASENSE, Inc.
Ground-Coupled Antennas
1.5 GHz 500 MHz
INFRASENSE, Inc.INFRASENSE, Inc.
Equipment Summary
• Antennas have become more compact
• Electronics have become more stable
• Range of frequencies has expanded
– Provides higher resolutions, greater depths of
penetration
INFRASENSE, Inc.INFRASENSE, Inc.
Software and Data
Interpretation
INFRASENSE, Inc.INFRASENSE, Inc.
Principles of GPR Application
Antenna
1 2 3
1
2
3
Air
base
Subgrade
Volts
Time Measurement Setup
GPR Record
Asphalt
INFRASENSE, Inc.INFRASENSE, Inc.
Sample of Data
Asphalt
Layers
Base
Layers
Ta
Tb
Pavement Structure
GPR Record
Time (ns)
INFRASENSE, Inc.INFRASENSE, Inc.
Sample Graphic GPR Data
Asphalt
Base
Pavement Surface
Time/depth
distance
INFRASENSE, Inc.INFRASENSE, Inc.
Sample Processed Graphic Data
on Asphalt Pavement
Asphalt
Base
Pavement Surface
INFRASENSE, Inc.INFRASENSE, Inc.
Linear Plot of Pavement Layer
Thickness
0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40
Mile Marker
0
5
10
15
20
Dep
th (
in)
Asphalt Layers
Base Layer
Cores
INFRASENSE, Inc.INFRASENSE, Inc.
GPR Data for PCC Pavement
Bottom of Base
Bottom of PCC Joints
INFRASENSE, Inc.INFRASENSE, Inc.
Typical Pavement Structure
Data Analysis
Bottom of Base
Bottom of AC
INFRASENSE, Inc.INFRASENSE, Inc.
GPR Data with Unclear
Interpretation
ACAC? Base?
AC
INFRASENSE, Inc.INFRASENSE, Inc.
Software/Interpretation
• Software developments have facilitated
quantitative analysis
• Some interpretation is still required to
distinguish layer types
• Fully automated processing is available for
limited applications (density, FWD)
INFRASENSE, Inc.INFRASENSE, Inc.
Pavement Applications
INFRASENSE, Inc.INFRASENSE, Inc.
Pavement Applications of GPR
• Pavement Management (Network)
• Rehabilitation Design (Project)
• Quality Assurance of New Pavement
Construction (thickness, density)
• Subsurface Moisture/Drainage
• Location of Dowels
• Detection of Asphalt Stripping
INFRASENSE, Inc.INFRASENSE, Inc.
GPR for Pavement Management
• Layer structure data for PMS
• Layer thickness for network FWD
• 100-200 lane miles per day coverage
• Results typically at 0.1 mile intervals
INFRASENSE, Inc.INFRASENSE, Inc.
Rehabilitation Design
• Existing thickness for overlay design
• Bound layer thickness for design of in place
recycling depths
• Thickness used with FWD data
• Locate areas of high moisture for drainage
design
• Locate subsurface damage
INFRASENSE, Inc.INFRASENSE, Inc.
Accelerated Rutting from
Clogged Drains
INFRASENSE, Inc.INFRASENSE, Inc.
View of Clogged Drain
INFRASENSE, Inc.INFRASENSE, Inc.
Detection of Drain with GPR
INFRASENSE, Inc.INFRASENSE, Inc.
Base Moisture Content from GPR
0%
2%
4%
6%
8%
10%
12%
14%
16%
133+00 143+00 153+00 163+00 173+00 183+00
Station
Est
imat
ed B
ase
%W
C
SB GPR
NB GPR
NB Cross Sections
SB Cross Sections
NB Lab Data
SB Lab Data
INFRASENSE, Inc.INFRASENSE, Inc.
Future Prospects for GPR• Equipment
– More compact, portable (wireless) equipment
– Implementation of antenna arrays
– Increased frequency range for depth/detail
• Software
– more automated, user friendly
• Applications
– Improved detection capability for expanded
applications