Potential Problems on I-77 Concrete Culvert

About the report:

Along a section of Interstate 77 in Carroll County, it was necessary to construct a fill approximately 256 ft deep. The flow of a mountain stream had to be carried through this massive embankment and, because of the nature of the terrain, it was decided to use a temporary steel culvert and a permanent concrete culvert. Deflection gage data were obtained up to a fill of 256 ft for the steel pipe and up to 125 ft for the concrete pipe, and deformed cross sections of the culverts were plotted for the various fill levels. Knowledge of the deformed cross section also permitted the determination of the circumferential bending moments. Plots were made of crown deflection versus fill depth. Research personnel who took deformation readings inside the steel culvert after the fill had been completed reported no plate tearing nor serious bolt tipping. However, the pipe underwent severe local plastic deformation in the region of the crown. The concrete pipe exhibited rather serious cracking and spalling at longitudinal locations along the spring line. Settlement curves provided detailed information concerning the amount and rate of settlement in the vicinity of the concrete culvert. As of October 1976, both culverts were still intact and useful, although efforts were under way to improve the condition of the concrete culvert before abandoning the temporary steel pipes. This report offered the following recommendations concerning the deterioration of the concrete culvert. Structural repairs may be considered but at the least, the corrosive water should be neutralized to reduce the chemical deterioration. In future construction of concrete on which water from a nearby source has ready access to the overlaying straw, an alternate method of backfill should be used instead of the straw or imperfect trench method.

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