OceanaGold Corporation is planning to expand the Haile Gold Mine, first opened in 1827, with a new 900-foot-deep open pit that is expected to have a 13-year lifecycle. M3 called on KCI to design a new bridge over U.S. 601 to carry the new haul road that connects the new site to the nearby 524-acre tailings storage facility.
The structure was designed to carry the Caterpiller 785C off-highway mining truck that has 10-foot diameter and a gross machine operating weight of 550,000 pounds.
After an environmental lawsuit delayed the project for two years and resulted in realignment of the haul road, our team finalized the design of a 90-foot-long, 42-foot-wide bridge with a five-foot-wide pipe trough to carry slurry for the mining operations. Engineers used a 3-D grillage analysis to determine load effects on the structure. The bridge sits on 72-foot-long modified bulb tees spaced five feet apart with a 15-inch thick deck slab on top. A five-foot-tall bridge parapet ensures that bridge rails extend to the axel height of the design truck.
A specialized analysis was required to account for the 550,000-pound mining trucks—that’s about 7-1/2 half times the typical highway bridge design loads.
Jared C. Medlin, PEStructural Engineer
During the construction phase, KCI reviewed shop plans, provided plan clarifications, answered Requests for Information (RFI), and provided milestone inspections. Material testing and other construction inspection was provided by another firm and observed by SCDOT personnel. We also provided acceptance inspections of the prestressed concrete beams for the owner prior to the beams leaving the precasting yard. Our team also performed temporary falsework and girder erection plans on behalf of the contractor during construction. At the close of construction, engineers performed the final inspection and created the punchlist on behalf of the owner and SCDOT.