Concrete Fills Annular Space Between the Excavated Rock and Steel Tunnel Lining at Arch Coal's Leer Mine
PITTSBURGH, PA — ELEMIX® concrete additive, an engineered Lightweight Synthetic Particle (LSP) that drastically and uniformly reduces the weight of concrete, was used for a 1,700-foot-long, 26-foot-wide mine slope built by Arch Coal, Inc. in Grafton, West Virginia.
The new Leer Mine (formerly referred to as Arch’s Tygart Valley # 1 Mine) will be a world-class underground coal mine and processing facility. It is expected to produce 3.5 million tons of premium metallurgical coal each year and employ more than 300 people.
The concrete, rendered lightweight by the ELEMIX additive, was used to fill the annular space between the excavated rock and the steel tunnel lining. The slope will provide a means of removing the coal, access for materials and equipment, and a secondary means of access / egress for mining personnel.
Approximately 75,000 lbs. of ELEMIX was used as part of a total volume of 8,000 cubic yards of concrete. The slope has a 12 percent downgrade.
“We used ELEMIX for several benefits,” says Frank Stevens, Construction Manager for Cowin & Company, Inc., a mining construction firm founded in 1924 and based in Birmingham, AL. “The lightweight concrete provided a strong backfill material at about 1/3 the density of normal concrete. The lower density allowed for rapid and continuous placement of the backfill without overloading the forms, saving substantial labor and overhead cost. We were impressed that the ELEMIX concrete flowed long distances without segregation or bridging, insuring complete backfill of the tunnel lining and consistent compressive strength.”
Kevin Foody, PE, LEED AP, Business Development Manager for ELEMIX says the company was very pleased to be a part of this project: “ELEMIX has been engineered to perform in exactly these types of applications. The particle size and density provides the material properties to contribute to the plastic and hardened performance of the concrete. “
Arch Coal renamed the Tygart Valley # 1 Mine in honor of Steven F. Leer, the company’s CEO for two decades, who recently was elected executive chairman of Arch’s board in April 2012.