TRC1504: Alternative Uses of Ground Penetrating Radar in Highway in Construction and Maintenance. Elisha Wright-Kehner, P.E.

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1 TRC1504: Alternative Uses of Ground Penetrating Radar in Highway in Construction and Maintenance Elisha Wright-Kehner, P.E.

2 Why GPR? Practicality Non-invasive (Non-destructive Testing - NDT) Real-time results Continuous data collection Very fast data collection Ease of use Accuracy & Precision Various levels of resolution and depth Works with almost every earth material Progressive advances

3 Ground-Penetrating Radar GPR is a non-destructive imaging tool that employs electromagnetic (EM) waves. Antenna Console DMI Cables GPS Power Source

4 AHTD Equipment Air-launched Ground-coupled 2010 SIR-30 (4 Ch.) Upgraded Antennas (2 GHz) GPS Highway Speeds Project & Network Level May TRC 1504 SIR-4000 (1 Ch.) 200, 400 MHz 1.6 GHz GPS Walking speeds Project level

5 Pavement thickness Uses Voids (Air or water-filled) Concrete cover - Bridge deck thickness* Rebars, Dowel bars* Utilities and USTs* (UXOs) Drains and sewer lines* Forensics/Cemetery/Burial sites Concrete/Rebar deterioration/spalling/delamination Changes in pavement density Bedrock depth/geotechnical studies Subsurface/Ground-water contamination Seepage pathways and sinkholes in levees Variation in mineral concentrations

Texarkana D3 Pile locating* o LR - SUR UST locating o o o Hot Springs - ROW Solgohachia -

6 In-house Projects May 2016 Feb 2017 Utility locating o Broadway Bridge ROW-Utilities Bridge deck thickness & Rebar mat depth (**) o Springdale - BRI Dowel bar misalignment o Texarkana D3 Pile locating* o LR - SUR UST locating o o o Hot Springs - ROW Solgohachia - ENV Desha - ENV Locating septic lines o Hampton ROW Asphalt & Subgrade thickness o Rogers - SIR

7 Texarkana First project with Ground Faulting slabs on I-30 Dowel bar alignment 1.6 GHz antenna 6 locations hours Satisfactory results Location 1 Location 2

8 Hot Springs UST detection 400 MHz

9 Broadway Bridge Utilities 400 MHz 350 HS* 300/800 DF* 3 months

10 Broadway Bridge 7 utilities 6 not on the plans

11 Hampton Sewer Lines 400 MHz Calhoun Co Water Lines

12 Solgohachia Historic well UST/Fuel Iines Water lines

13 Desha USTs 400 MHz

14 Springdale Bridge Deck & Concrete Cover Thickness First Project using dual systems o Ground GHz o Air - 2 GHz

15 Springdale 0.38 inches accuracy concrete cover ~1 inch underestimated deck thickness on average

16 Rogers Asphalt and subbase thickness First Project using ground antenna with air-launched system o Ground 400 MHz o Air - 2 GHz

17 Rogers

Resolution and depth of penetration Metal bridges and elements Depth is dielectric constant

18 Limitations Water content o High moisture content o Shallow water table Clay Concrete utilities Rough terrain (ground-coupled) o Obstacles Radio frequencies interference GPS connection Resolution and depth of penetration Metal bridges and elements Depth is dielectric constant dependent TDEMI - SHRP2 Implementation R01B?? Wikipedia.org Dry Weather Clean/even Surface Workable Space

19 Questions?

A typical GPR survey Antenna selection Depth and Resolution o 200 MHz 15-20 ft o 400 MHz 8-10 ft o 1.

20 A typical GPR survey Antenna selection Depth and Resolution o 200 MHz ft o 400 MHz 8-10 ft o 1.6 GHz 1-2 ft o 2 GHz 1-2 ft Pre-existing plans o Planning o o o Location and extent of utilities/usts 2D 3D Super-3D Survey area is always larger than requested! Assembly mins o 1-2 persons Calibration o o Metal plates Dielectric measurements Cores/Ground-truth data Data processing & Interpretation

21 Discontinuities Distance Depth Time

22 Utility Lines Distance Depth Time

23 Utility Lines Distance Depth Time

Ground-Penetrating Radar 1 Dielectric Constant Dielectric (GPR) Constant 1 11 21 31 41 51 61 71 81 1 1 11 21 31 41 51 61 71

24 Ground-Penetrating Radar 1 Dielectric Constant Dielectric (GPR) Constant Rel. Velocity (m/ns) Rel. Velocity Velocity(m/ns)

25 Ground-Penetrating Radar 1 Dielectric Constant (GPR) Dielectric constant Rel. Velocity Velocity Velocity of EM wave relative to Speed of Light Velocity(ft/ns)

26 GPR Theory EM properties of materials 1. Dielectric Constant, ε 2. Electrical Conductivity, σ 3. Magnetic Permeability, µ R = εε 2 εε 1 εε 2 + εε 1 υ = cc εε rr AA = AA 0 ee αααα c = 983,571,056 (ft/sec)

Material Water content ε σ GPR Theory Dielectric Constant Sand (dry) 3-6 Sand (saturated) 20-30 Silts 5-30

(saturated) 19 Clayey soil (dry) 2 Clayey soil (saturated) 15 Sandstone (saturated) 6 Limestone (dry) 7

27 Material Water content ε σ GPR Theory Dielectric Constant Sand (dry) 3-6 Sand (saturated) Silts 5-30 Shales 5-15 Clays 5-40 Humid soil 30 Cultivated soil 15 Rocky soil 7 Sandy soil (dry) 3 Sandy soil (saturated) 19 Clayey soil (dry) 2 Clayey soil (saturated) 15 Sandstone (saturated) 6 Limestone (dry) 7 Limestone (saturated) 4-8 Basalt (saturated) 8 Granite (dry) 5 Granite (saturated) 7 Frequency Frequency Resolution Depth

28 Layered Medium Distance Depth Time

29 Discontinuities Distance Depth Time

30 Utility Lines Distance Depth Time

31 Utility Lines Distance Depth Time

32 Data Collection Practices 2D 3D 3D Super-3D

33 ε 1 ε 2 ε 1 ε 1 ε 2 ε 2 ε 2

34 ε 1 ε 2 ε 2 ε 1 ε 1 ε 2 ε 3 ε 2 ε 2

35 ε 1 ε 2

36 ε 1 ε 2

37 ε 1 ε 2

38 Utility Lines Distance Depth Time

39 GPR Theory Transmitter Receiver Amplitude Transmitted Wave ε 1 σ 1 μ 1 Reflected Wave ε 2 σ 2 μ 2 Time

40 Wavelength vs Dielectric Constant Wavelength (ft) MHz 400 MHz 1.6 GHz 2 GHz Dielectric Constant

41 GPR Theory Velocity (ft/ns) Air Dielectric constant Water Water Content ε σ Frequency Resolution Frequency Depth Wavelength (ft) MHz 200 MHz 400 MHz Wavelength (ft) MHz 1000 MHz 1.6 GHz 2 GHz Dielectric Constant Dielectric Constant

42 Material Water Content ε σ Frequency Frequency Dielectric Constant Sand (dry) 3-6 Sand (saturated) Silts 5-30 Shales 5-15 Clays 5-40 Humid soil 30 Cultivated soil 15 Rocky soil 7 Sandy soil (dry) 3 Sandy soil (saturated) 19 Clayey soil (dry) 2 Clayey soil (saturated) 15 Sandstone (saturated) 6 Limestone (dry) 7 Limestone (saturated) 4-8 Basalt (saturated) 8 Granite (dry) 5 Granite (saturated) 7 Resolution Depth Velocity (ft/ns) Wavelength (ft) GPR Theory Dielectric Constant Dielectric constant 200 MHz 400 MHz 1.6 GHz 2 GHz Velocity(ft/ns)

43 Wavelength (ft) MHz 400 MHz 1.6 GHz 2 GHz Air Dielectric Constant Water

44 Material Water Content ε σ Frequency Dielectric Constant Sand (dry) 3-6 Sand (saturated) Silts 5-30 Shales 5-15 Clays 5-40 Humid soil 30 Cultivated soil 15 Rocky soil 7 Sandy soil (dry) 3 Sandy soil (saturated) 19 Clayey soil (dry) 2 Clayey soil (saturated) 15 Sandstone (saturated) 6 Limestone (dry) 7 Limestone (saturated) 4-8 Basalt (saturated) 8 Granite (dry) 5 Granite (saturated) 7 Resolution Wavelength (ft) Velocity (ft/ns) GPR Theory Dielectric constant Velocity(ft/ns) 200 MHz 400 MHz 1.6 GHz 2 GHz Frequency Depth Dielectric Constant

Geophysics for Environmental and Geotechnical Applications

Geophysics for Environmental and Geotechnical Applications Dr. Katherine Grote University of Wisconsin Eau Claire Why Use Geophysics? Improve the quality of site characterization (higher resolution and