Award of Merit: Special Projects Category
Kennecott Humboldt Mill Structural Strengthening
Submitted by PULLMAN
Kennecott Eagle Minerals Company
The Humboldt Mill has been idle since the 1990s. The recent discovery of a large deposit of nickel and copper has led to the rehabilitation of the facility. Starting in the summer of 2014, ore will be hauled from the mine site to the mill, where separate nickel and copper concentrates will be created and transported via rail for further refinement. This project will be Michigan’s first newly constructed mine in decades and will also be the only primarily nickel-producing mine in the United States.
An integral part of the reconstruction efforts was in the fine ore bin area of the concentrator building. This area is used to store crushed ore in bins located on the mezzanine level, approximately 24 ft (7 m) above grade, weighing in excess of 2 million lb (907,000 kg) empty. Given the extreme load created by the bins and the ore they will contain, it was determined that the existing support structure was insufficient.
The existing structure required strengthening in the form of column enlargements and foundation reconstruction. Many challenges were overcome throughout the course of the project, including extremely cold weather, an aggressive schedule, and a congested work site. In all, the project included 16 column enlargements, eight new columns, four reconstructed and enlarged foundations, and 24 newly constructed column caps.
The columns were placed with self-consolidating concrete (SCC)—a highly flowable, nonsegregating concrete that fills formwork and encapsulates congested reinforcing without mechanical vibration—while maintaining significant compressive strength. A mockup column enlargement was performed to test the material and the formwork design.
Being a Mine Safety and Health Administration (MSHA) site, safety was of the utmost importance and over 11,000 man-hours were completed without incident or injury.