IBTTA Facilities Management and Maintenance Workshop Nashville, Tennessee

Transcription

1 IBTTA Facilities Management and Maintenance Workshop Nashville, Tennessee High-Speed Nondestructive Testing Methods for Mapping Voids, Debonding, Delaminations, Moisture, and Other Defects Behind or Within Tunnel Linings SHRP2 R06(G)

2 IBTTA Facilities Management and Maintenance Workshop Nashville, Tennessee Texas A&M/TTI - Andrew Wimsatt, Tom Scullion, Stefan Hurlebaus, Dan Zollinger University of Texas at Austin - Fulvio Tonon German Federal Institute for Materials Research and Testing (BAM) -Parisa Shokouhi, Herbert Wiggenhauser University of Texas at El Paso Soheil Nazarian Roadscanners - Timo Saarenketo

3 Introduction Tunnels service high traffic volumes and operate in aggressive environments Timely detection and remediation of problems requires periodic inspection to assess structural condition over time Condition and deterioration rate is key to determining the appropriate schedule of maintenance and/or rehabilitation Keeping tunnels open during inspection is an issue Minimize tunnel closures and user delays Must balance need to conduct detailed inspections to ensure user safety Objective of investigation - the identification and review of NDT methods for conditions assessment of tunnel linings Applicability, advantages and limitations of the investigated methods

4 Content Laser Scanning: SPACETEC Tunnel Scanner Thermal Camera (IR Camera) Systems Ultrasonic Linear Array (MIRA) Digital Photogrammetry Ground Penetrating Radar (GPR) Impulse Response (IR) and Impact Echo (IE) Ultrasonic Surface Waves (USW) Percometer Dielectric Probe Technique Concrete Surface Resistivity Testing Ultrasound Structural Health Monitoring

5 Laser Scanning: SPACETEC Tunnel Scanner [ Applications Document condition at delivery of new construction Survey tunnel prior to reconstruction or renovation measures Check tunnel clearance before electrification, the use of new vehicles, or before the transport of excessive loads Conduct regular inspections for the early identification of damage and for planning repairs Allow for detailed data analyses with thermographic recordings or crack charting

6 Laser Scanning: SPACETEC Tunnel Scanner Advantages High-speed collection Analysis of data from three different, simultaneous measurements Delivers high resolution images 360 coverage Limitations Cost Size

7 Imaging Systems (Spacetec)

8 Imaging Systems (Spacetec)

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15 Spacetec Profile recordings - Critical points are displayed on the screen, where they can be localized and the areas and volumes can be computed. Visual recordings are needed mainly for routine checks and for documenting the tunnel surface. The scaled data allows lengths, areas, and volumes to be determined accurately

16 Spacetec Thermographic recordings give indications of structural damage that is not visible to the naked eye, for instance water, cavities, or fluctuations in density in the tunnel lining. SPACETEC also carries out special and customized data analyses, for instance crack charting or detailed interpretation of thermographic recordings.

17 Examples of Costs Germany Scanning 2 tunnel sections (each 1 km long), including thermography measurements, data pre-processing and analysis costs about 30,000. Cost per tunnel-km is then 15,000. Testing 100 tunnels in Europe, together about 100 km long, requiring 3 weeks of measurement, including data preprocessing and analysis costs 250,000. Cost per tunnel-km is then only 2,500.

18 Speed As high as about 100 km/hr for coarse measurement needs As low as 2 km/hr for very detailed investigations. The typical measurement speed is usually in between these two extremes (~5 km/h). Chesapeake Bay Tunnel ~ 2 km/h

19 Resolution Examples Low Speed High Speed

20 Data collected in Chesapeake Tunnel, VA, USA, April 11, 2011 Inspection vehicle

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22 Data collected in Chesapeake Tunnel, VA, USA, Visual Image

23 Data collected in Chesapeake Tunnel, VA, USA, IR Image

24 Data collected in Chesapeake Tunnel, VA, USA, Visual and IR Image

25 Data collected in Chesapeake Tunnel, VA, USA, Detail

26 Data collected in Chesapeake Tunnel, VA, USA, Detail

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28 Data collected in Chesapeake Tunnel, VA, USA, Detail

29 Vent in Ceiling Ceiling Railing Area of Concern Niche for Fire Extinguisher

30 Area of Concern Construction Joint

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34 Thermal Camera (IR Camera) Systems Applications Locate voids under roadway surfaces Detect distress in concrete and asphalt pavements Detect moisture inside or under AC pavements Aid in quality control/assurance of asphalt pavements Monitor areas affected by freeze-thaw weakening

35 Thermal Camera (IR Camera) Systems Advantages Best used along with air-coupled GPR on fast moving vehicle Quickly covers wide areas Easy to interpret results and quickly make maps System can be used in other road and bridge surveys Associated cost is relatively low. Limitations Dust may interfere with readings

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40 Digital Photogrammetry Capture Images Determine Camera Orientations Generate DTMs Analyze data: calculate volumes, digitize vector data, etc. Applications Monitor deformations along tunnel linings Determine fracture trace lengths Condition assessment and inspection Aggregate characterization

41 Digital Photogrammetry Advantages Measurement speed Low cost Easy to transport equipment; small and lightweight cameras 3D modeling Offers 100% coverage No need for specially trained personnel Limitations Collects data for objects within a straight line-of-sight, meaning pictures must be taken from multiple vantage points to avoid possible obstacles Measurements can be influenced by air temperature and pressure, requiring corrections for atmospheric effects

42 Ultrasonic Linear Array (MIRA) Applications Detection and characterization of cavities, flaws, cracks, honeycombing, and grouting defects in or behind tunnel lining Locate tendon ducts and reinforcement bars within concrete Measure concrete member thickness Assess the quality of crack repairs

43 Ultrasonic Linear Array (MIRA) Advantages Dry-point contact Real-time 2D imaging Applicability on rough surfaces See beyond reinforcement Fast data collection Capable for automatic areal coverage Limitations Testing requires physical contact with surface Limits collection speed (even when mounted on scanner) Test object cannot be less than 50mm thick Shallow defects at depths less than 50 mm cannot not be detected

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49 23 mm from surface

50 64 mm from surface

51 78 mm from surface

52 80 mm from surface

53 103 mm from surface

54 127 mm from surface

55 131 mm from surface

56 148 mm from surface

57 150 mm from surface

58 167 mm from surface

59 Ground Penetrating Radar (GPR) Ground-Coupled Systems Applications Measure concrete wall thickness Detect voids between concrete and test grouting Identify water leakage and movement behind linings and pavements Detect cables and pipes

60 Ground Penetrating Radar (GPR) Ground-Coupled Systems Advantages Good penetration depth Ability to map areas with high moisture content Calculate area of risk for corrosion Limitations Low measurement speed Lengthy data processing Not for use when tunnel is made of steel reinforced shotcrete

61 Ground Penetrating Radar

62 Ground Penetrating Radar

63 Ground Penetrating Radar (GPR) Air-Coupled Systems GPR Horn Antenna Systems for Tunnel Surveys Applications Pavement evaluation and forensic investigations Could be possibly used for routine monitoring of tunnel walls and roofs to find changes in electrical properties that indicate potential problems

64 Ground Penetrating Radar (GPR) Air-Coupled Systems Advantages Surveys can be done from a relatively fast moving vehicle Measurements are accurate and repeatable Analysis works wells along with thermal cameras System is well suited for routine monitoring of tunnel walls and roofs Limitations Sensitive to variation in antenna-to-wall distance Sensitive to external radiation (such as cell phone stations) Less penetration depth than ground coupled GPR Not for use when tunnel is made of steel reinforced shotcrete

65 Air Coupled Ground Penetrating Radar

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67 Air Coupled GPR Antenna Data

68 Air Coupled GPR Antenna Data

69 Ultrasound [Taffe and Gehlen, 2008] Applications Correlate material strength to standard strength Determine thickness of tunnel lining Locate cracks, voids, deteriorations

70 Ultrasound Advantages Conventional ultrasonic equipment is readily available Fairly inexpensive Offers 100% coverage Allows for continuous monitoring Limitations Conventional equipment must be in contact with object Some issues in the past with poor repeatability and/or consistency Long waits between scan locations due to reinstallation of transducers

71 Impulse Response (IR) and Impact Echo (IE) Applications Detect delamination of linings Detect voids behind linings Determine thickness of tunnel linings

72 Impulse Response (IR) and Impact Echo (IE) Advantages Results obtained onsite Results determined quickly ( 1 minute) Limitations Testing is discrete (pointwise) Not feasible for rapid, 100% coverage testing Cannot provide properties of deeper layers if cosmetic layer is not fully bonded

73 Ultrasonic Surface Waves (USW or SASW) [Nazarian et al., 2006] Applications Measure modulus and strength concrete Estimate condition of concrete Detect delamination, debonding and loss of strength due to internal cracking of concrete

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75 Ultrasonic Surface Waves (USW) Advantages Reduces number of destructive tests required Results determined quickly ( 1 minute) Provides qualitative variation of modulus with depth Moisture has small impact on results (ideal for tunnels) Limitations Testing is discrete (pointwise) Not feasible for rapid, 100% coverage testing Cannot provide properties of layers beyond debonded layers

76 Percometer Dielectric Probe Technique [Scullion and Saarenketo, 1997] Applications Detect free moisture in concrete walls (directly or through tiles) Determine dielectric permittivity of asphalt surfaces

77 Percometer Dielectric Probe Technique Advantages Surface, concave and tube probes for multiple applications Easy to use Fast results Limitations Point measurement Surface probes require relatively flat surfaces for reliable results May not work on shotcrete concrete

78 Dielectric Probe

79 Dielectric Mapping

80 Concrete Surface Resistivity Testing Applications Resistivity measurements may give indication of corrosion Estimate rate of corrosion Assess permeability

81 Concrete Surface Resistivity Testing Advantages Generally good correlation between surface resistivity and corrosion potential Limitations May not be able to measure resistivity accurately on concrete surfaces due to affect of carbonation on surface resistance Slow and point specific 60+ seconds per test location

82 Scanning Systems

83 Scanning Systems

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86 Structural Health Monitoring Level 2 Level 1 Base Used tree branches Alternative branches Applications Allows autonomous damage detection Monitor strain of tunnel lining, changes in tilt angles Monitor environmental parameters (temperature and humidity)

87 Structural Health Monitoring Advantages Continuous inspection, as opposed to scheduled inspection Autonomous No lane closures required Fairly inexpensive equipment allows for permanent installation Limitations Sensors require power Note this technology will not be field tested under SHRP2R06G

88 Conclusions Reviewed and evaluated different nondestructive testing methods for tunnel inspection To minimize traffic disruption, it is necessary to use NDT techniques for high-speed testing of tunnel linings Good, high-speed options SPACETEC scanner combined use of thermal cameras with air-coupled GPR With consistent advancement of NDT, current methods will continue to improve and new methods will continue to be developed to aid in tunnel inspections