Mapping Voids, Debonding, Delaminations, Moisture, and Other Defects Behind or Within Tunnel Linings (2013) / Chapter Skim
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Pages 53-65
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53 a p p e N D I x I Introduction Since 1982, SPACETEC has offered a scanner system to monitor disruptions and conditions of tunnel linings (Figure I.1)
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54 Figure I.3. Visual image of conditions of a shotcrete lining in a motorway tunnel.
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55 concerned. At any time, later data can be consulted to look for changes in those conditions.
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56 • The influence of cold and warm temperatures, respectively, at the surface; • Surface roughness; • Cavities (gravel nests below the surface, bad contact of the lining to the rock, and gravel rock material) ; and • Nonhomogeneous material composition.
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57 Table I.1. Data Summary of the Chesapeake Tunnel Time of measurement April 11–12, 2011 Scanning length 1,680 m Vehicle speed Approximately 1.5 km/h Recording channel Infrared (8–12 µm)
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58 S N left ceiling right driving direction NS right left ceiling exhaust air port fresh air port cement conduits for power cables hand rail tunnel lighting driving direction Projection to a plane lane fire extinguisher niche electrical installation fire extinguisher niche & road sign swirled warm air Figure I.8. Perspective view (bottom)
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59 Figure I.11 shows one common type of damage -- broken or missing tiles -- which is clearly evident in the visual channel (upper left)
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60 A A B B Figure I.11. Views of broken or missing tiles.
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61 required heat flow conditions during the thermal measurement between the lining and the rock to resolve and interpret patterns of heat anomalies. Temperature sensors were placed in the target structure.
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62 temperature when the tunnel had proper air convection -- resulting from a chimney effect, caused by different air pressures between the tunnel portals, or from steady traffic. Long-term surveys of other tunnels revealed a number of good measuring conditions during a period of several months.
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63 Figure I.15. Air flow from port in tunnel ceiling.
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64 defective and loose tiles anomalies Figure I.17. Loose tiles (left)
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65 datasets: joints between the tiles showed a different reflectivity, which seemed to indicate renewed ceramic tiles. The main findings in the thermographic data set were these: • Cable channels and drainage tubes behind the linings with lower heat conduction; • Areas with lighter tile joints, maybe renewed or repaired tiles, with different materials and lower heat flow at the side walls; and • Areas with larger anomalies behind the ceiling walls.
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