By: Lane Enterprises
Restoration projects come in all shapes and sizes. The foundations for this active Rapid City, Pierre & Eastern Railroad bridge were performing well. To extend the service life of the foundations, engineers decided to protect the existing piers by drilling micro piles extending into the shale bedrock below.
These piles were advanced a minimum 20 feet to provide deep and stable support for the existing bridge piers. Several feet of the channel bottom were removed around the foundations to allow the toe of the corrugated steel caisson sheets to be buried after installation and to fully encase the existing pier structures. The structural plates sections were sized to allow enough clearance and spacing for the double mat of reinforcing steel.
After the galvanized structural steel plates were assembled, bolted together, and tightened, they were ready for the placement of concrete. The contractor elected to place the nuts of the bolts on the inside of the structural plates forms for consistent esthetically pleasing exterior finish. The concrete was placed in the forms, consolidated, and allowed to cure around the existing bridge supporting piers.
New cast in place, steel reinforced concrete caps were placed over each protective corrugated steel form. The stream bed around the new protective forms was backfilled and reshaped to maintain its hydraulic capacity during peak events.
Much of the rehabilitation work occurred in February 2022.