AASHTO Journal, 4 September 2015
Some drivers heading north on Interstate 65 out of Lafayette, Ind., have been dealing with a long detour throughout August that might cost them as much as an extra hour, news reports say. But the Indiana Department of Transportation said its contractor projects that a damaged I-65 bridge should reopen to traffic by mid-September.
INDOT said the bridge was first closed Aug. 4 when contracting crews on a highway expansion project noticed “unusual movement” in the bridge.
After repairs with temporary supports to a bridge pier, traffic was allowed to resume the next day, but the agency on Aug. 7 said engineers again “noticed movement in the same vertical riverbank pier” and ordered the bridge re-closed. News reports described a visible “dip” in the bridge.
That soon became a time- and money-consuming disruption to northbound passenger and freight traffic trying to get around the jam, with trucking industry sources complaining of a detour of more than an hour.
By Aug. 19 INDOT said its designated detour route over U.S. and state roads “maximizes use of four-lane roads and minimizes traffic signals,” and that it took a number of measures to improve traffic flow – including dynamic messages as far south as Louisville, Ky.
The agency said its efforts reduced the detour to about 9 miles and 25 minutes of travel time. And it reminded travelers that some could opt out of highway travel and use daily round-trip Amtrak rail service between Indianapolis and Chicago.
That Aug. 19 announcement also explained what had caused the bridge problem, and what was being tested to fix it.
INDOT said it had awarded an $82.8 million design-build contract in January to a contractor to widen and rehabilitate a section of I-65 in Lafayette. As part of that work, construction crews drove steel piles into soil to widen the existing piers, and sheet piling to work below the waterline of Wildcat Creek that the bridge spans.
“The piles pierced the water-tight soils to a sandy layer with water under pressure,” the release said. “Sand and/or water percolated up from beneath the bridge pier, causing it to tilt. Structural engineers monitoring the riverbank pier noticed the pier settling and tilting, and ordered the bridge closed on Aug. 7 in the interests of safety.”
The expected fix had specialized crews testing the use of deeply drilled, high-strength but small-diameter “micropiles” through the footings of the existing pier, the agency said.
“The process involves drilling steel casings through the water-tight soils, injecting grout to fill and densify the sandy soils below, and then installing the micropiles.” INDOT added that “micropiles have been used effectively to stabilize other bridge piers around the country.”
