Use of Radar in Pavement Evaluation and Forensics
Use of Radar in Pavement Evaluation and Forensics
Use of Radar in Pavement Evaluation and Forensics
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Introduction• Ground Penetrat<strong>in</strong>g <strong>Radar</strong> (GPR)Development• Applications• Case Studies
Texas Ground Penetrat<strong>in</strong>g<strong>Radar</strong> (GPR) Development
<strong>Radar</strong> Systems Development• Research Project 930– 1991, SHRP site layer thicknessdeterm<strong>in</strong>ation• Research Project 1923– 1992, Influence <strong>of</strong> surface on layer thickness• Research Project 1233– 1992 (Rev 1994), “Implementation <strong>of</strong> theTexas Ground Penetrat<strong>in</strong>g <strong>Radar</strong>”
TxDOT’s GPR Development Effort• 87 - 88 GPR first demonstrated to TxDOT• 89 - 90 <strong>Evaluation</strong> + Specification Development• 90 - 99 S<strong>of</strong>tware Development- Research systempurchased - numerous research studies• 95 – 96 TxDOT purchases first system• 96 – 04 Tra<strong>in</strong><strong>in</strong>g schools• 96 - 04 <strong>Pavement</strong> design, Forensic Investigations• 00 – 02 Buy additional units• 02 – 04 Integrat<strong>in</strong>g GPR <strong>and</strong> FWD• 00 – 04 Quality Control Studies• 02 – XX Fight<strong>in</strong>g with Feds
This was the mostenjoyable presentation <strong>of</strong>the day!
<strong>Radar</strong> Systems Development• Texas Ground Penetrat<strong>in</strong>g <strong>Radar</strong> (GPR)– TTI, Texas A&M (1 unit)– TxDOT, Construction Division (4 units)• Ground Coupled radar systems– GSSI
GPR Characteristics
GPR Characteristics• Air Coupled– Up to highway speeds (65 mph)– Long distances– Readily analyzed– Low traffic exposure• Ground Coupled– Creep speed– Specific area <strong>in</strong>vestigations– Needs more <strong>in</strong>tensive analysis
GPR Characteristics• Air Coupled– 24” depth• Ground Coupled– 1GHz -- 24”– 500 MHz -- 15 ft– 200 MHz -- 30 ft– 100 MHz -- 100 ft
<strong>Radar</strong> Systems DevelopmentAir Coupled Systems DevelopmentDigital Dual ComputerS<strong>in</strong>gle ComputerDigital VideoAnalog/Mono-staticAnalog/Bi-staticAnalog Video
<strong>Radar</strong> Systems DevelopmentDigital Dual Computer System• GPR Collection System– Controller– Antenna• Video Collection System– Computer–Camera• Ancillary– Distance Measurement–GPS
Air Coupled GPR System
Digital Dual Computer System
Ground Coupled GPR System
This was the mostenjoyable presentation <strong>of</strong>the day!
USE IT• GPR Signal• GPR Representation• Applications
Inside the Bi-static antenna• Two Tapered horns• Pulse Generator(transmit antenna)• Sampler (receiveantenna)
Basics <strong>of</strong> GPR4v10 v2v1 v4v2v1v6v2v2 ns 5.2 nsAssumes zeroattentuation
Dielectric Measurements• Air0 (1)• Water81
COLORMAPGPR data from athick Hot Mixsection with nodefects
So,What can it do?
Successful GPR Applications• Thickness <strong>of</strong><strong>Pavement</strong> Layers• Changes <strong>in</strong> structure• Defects <strong>in</strong> Base (Wetareas)• Defects <strong>in</strong> Hot Mixlayers (stripp<strong>in</strong>g,trapped moisture)• Segregation <strong>and</strong> poorjo<strong>in</strong>t density• Deteriorated bridgedeck overlays• Base wash-outs• Water filled voidsunder PCC
Exotic GPR Applications• Location <strong>of</strong> s<strong>in</strong>k holes• Ab<strong>and</strong>oned tanks• Buried Rt 66 Signs• Overlayed manholecovers• Reta<strong>in</strong><strong>in</strong>g wall<strong>in</strong>tegrity• Utility pipe bursts• Grave sites
Thickness Determ<strong>in</strong>ationsOutside LaneAt top <strong>of</strong>embankmentApprox 4<strong>in</strong>7.5 – 9.5”16”19”CurveRiver BridgeOltorfOverpassWoodl<strong>and</strong>Overpass
Section Breaks
GPR data from thick HMA section with subsurface damage
Low density & debond<strong>in</strong>gVoided areas, vertical segregation, & debond<strong>in</strong>gIH 35 San Antonio
SH 114 Fort Worth..GPR & AV comparisonsSF mixes% A ir V o id0 10 20 30 400T y p e C2Type C & B mixes84 6T y p e B10 1214(R B L )1618F W 02 8
<strong>Use</strong> <strong>of</strong> GPR todetect Segregation
Water L<strong>in</strong>e Rupture
TTI <strong>Radar</strong> Systems
Water L<strong>in</strong>e Blow OutsTV VideoPipe 10 ft deep
Void locationNormal
IH 35 Aust<strong>in</strong>Easter 2002TV VideoOvernight collapse<strong>of</strong> ma<strong>in</strong> lanes
VIDEO
Best <strong>of</strong> the day!
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