EMBANKMENT INSTRUMENTATION TUNNEL PERFORMANCE

A corrugated metal tunnel for housing instrumentation is described which has performed outstandingly, and has minimized vandalism of instruments and equipment, eliminated the necessity to flush hydraulic piezometers with antifreeze during the winter, and reduced construction delays normally associated with test sections. A figure is presented which illustrates the 110-ft long, 5-foot diam., flexible steel-plate tunnel. After installation of instruments, the tunnel was placed on the working surface which sloped away from the center line and was then covered. The alinement of the tunnel and the placing of the instrumentation is briefly outlined. The 5-ft diam. pipe was constructed from 8-gage, asbestos bonded, multiplate corrugated metal and the 8-in diam. vent pipe was constructed from 12-gage, asbestos-bonded-corrugated metal. Slots in the bottom of the tunnel for the instruments were cut and positioned over the instrumentation in the field. The tunnel is illuminated by a permanent lighting system powered with a portable generator. After 5 yr. of service, the tunnel has shown no signs of distress. The encountered settlement indicates that the slope of the initial placement grade for tunnels should account for differential settlement to preserve adequate drainage. Risers from instruments founded in layers that do not settle will not settle with the tunnel. Therefore, provision should be made to remove sections of riser pipes for these instruments as the tunnel settles. Observations are made which relate to the horizontal diameters along the tunnel, and the culvert deformation. Measurements indicate that there is scatter in the present diameter which is probably the result of the fabrication technique. Although little corrosion has been observed in the liner, the instruments themselves have begun to corrode after 5 yr. of service. The connections between hydraulic piezometers risers and the tunnel were constructed with flexible plastic pipe. Recommendations are made which are based on practical experience and which relate to access to bench mark for settlement surveys, and the lock system.

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  • Accession Number: 00262735
  • Record Type: Publication
  • Report/Paper Numbers: Proc. Paper 10510 Tech. Note
  • Files: TRIS
  • Created Date: Nov 27 1974 12:00AM