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A $10.3 million project to replace the overpass at the junction of U.S. Highway 190 and Louisiana Highway 12 and four-lane 1.25 mi. of Highway 12 should be completed next spring.
Work on the Calcasieu Parish project began in October 2003 with the demolition of the existing 700-ft. overpass. The new overpass will be 1,100 ft. long, said field coordinator Jim Benoit of F. Miller and Sons Inc. of Lake Charles.
The neccessity of working around a railroad right-of-way running under the bridge has required a lot of schedule manipulation, Benoit said. All work has been coordinated with train traffic schedules.
"We had to secure a window with no train traffic just to set the girders," Benoit added.
To make the situation more complicated, when work is performed within 20 ft. of the railroad right-of-way, a Union Pacific representative has to be on hand to monitor the work.
"It has made the project a bit interesting," Benoit said.
A lack of drainage in the work area has been another concern. The site is located in an upland coastal plains area and there is little if any variation in elevation throughout the area.
"Every time it rains, it's a challenge to dry things out again," Benoit said. There have been roughly 100 rain days since the beginning of the project.
Throughout the project, traffic on Highway 12 will be diverted by a temporary bypass road.
"Presently, there are two ramps that bring traffic onto U.S. 190 from U.S. 171," Benoit said. "These ramps were rerouted to form detours around the four-laning project."
The old bridge was demolished using a 65-ton crane and a trackhoe. Roughly 1,800 cu. yds. of concrete were hauled to a nearby borrow pit.
The embankments for the existing overpass were removed by McManus Construction Inc. of Lake Charles. Owner Sheldon McManus said about 135,000 cu. yds. of dirt were excavated for the project using excavators and bulldozers.
About 300 ft. of new embankment was formed with 160,000 cu. yds. of soil imported from a borrow pit and then compacted and graded.
As foundation for the overpass, 55 drill shafts averaging 60 to 70 ft. deep and 66 in. diameter were formed using 1,200 cu. yds. of 4,000-psi concrete.
Benoit said a test shaft loaded with a Osterberg Load Cell was used to confirm the design load for the shafts. The test allowed engineers to determine the capacity of the shafts using a specialized pressure cell placed at the bottom of the shaft excavation. A hydraulic line extended from the cell to the top of the excavation.
After placement, the pier excavation was filled with concrete and instruments measured the upward and downward displacement of the cell.
Benoit said 45 19- to 20-ft. columns, each 48 in. in diameter, were poured directly on top of the drilled shafts using 4,000-psi concrete. Roughly 700 cu. yds. of concrete was poured to form the columns. The shafts were formed using steel column forms.
Concrete caps were placed on the columns and supported by through-bolt clamps. Forty-two-in., wide-flanged steel beams were then set in place.
About 105 precast concrete girders averaging about 25 tons each were supplied by Boykin Bros. Inc. of Baton Rouge.
Benoit said decking is being placed on a stay-in-place form made of 7- by 3-ft. steel sheets, and the driving surface will consist of 1,400 cu. yds. of 4,250-psi concrete provided by Dunham-Price Inc. of Lake Charles.
Concurrent with the construction on the interchange, the ramps and approaches are being constructed and a section Highway 12 is being four-laned near the bridge.
After the soil was processed by discs and self-propelled rollers, cement was cut into the bedding with an 8-ft.-wide stablilizer to a depth of 12 in. The bedding was recompacted using self-propelled rollers and then graded with a padfoot motor grader.
About 104,000 sq. yds. of Class II, 6/10 limestone base is being used for the road, McManus said. The base material is supplied by Port Aggregates of Lake Charles.
The riding surface will consist of asphalt supplied by Asphalt Products of Baton Rouge.
In July, 400 ft. of the overpass deck remained to be completed. The concrete barrier rail, which will be 15 in. at the base and 32 in. high, as well as a 40-ft. approach slab, were was also incomplete.
The base is currently being processed for the highway expansion portion of the project, Benoit said.
A 5-ft.-thick surcharge was placed at each end of the bridge to pre-compact the dirt header, Benoit said. The surcharge has to stay in place for 10 months for compaction.
Once that's accomplished, work can begin on the approaches.
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