As coal mines go, Alliance Resource Partners’ River View mine is a relatively new facility where four Volvo trucks keep pace with a high-production mine.
In 2010, its first full year of operation, the underground mine produced 5.8 million tons of clean coal. Since then, market conditions have allowed the mine to ramp up to more than a million tons of run of mine coal per month. The mine, located along the Ohio River near Evansville, Indiana, is known as the most productive continuous miner operation in the Illinois Basin.
At the mine, raw coal is conveyed to the surface and moves to a preparation plant. “From the plant we get clean coal, coarse refuse, and slurry, which is mostly water,” says Mark Henshaw, project engineer. “The coarse refuse is a waste product that consists of shale and fine clays. The refuse and slurry together are about 35 percent of the raw material feed.”
Clean coal is stockpiled and later loaded into barges for transportation on the Ohio River. The slurry is pumped to a 55-acre impoundment lake. Coarse refuse is conveyed to a 300-ton refuse bin located on a high hill next to the slurry lake.
What contains the slurry lake? A threesided dam made of the coarse refuse. The fourth side is an old refuse pile placed there years ago.
Depending on the trucks
The coal mine is a high-production operation, and so is the dam-building project. The mine produces coarse refuse at the rate of 285,000 tons per month – or 570 tons per hour. The refuse bin only holds 300 tons, so mine production relies completely on the trucks hauling refuse away from the bin.
That’s why River View Coal depends on four Volvo A40E FS articulated dump trucks to haul coarse refuse and build the 8,000-footlong impoundment dam around the slurry lake. “Our mining operations depend on those trucks to haul coarse refuse,” says Henshaw. “If one truck goes down, we can adjust. But if the trucks can’t run, the plant shuts down, and we’re in trouble.
“These trucks run 24/5 and do about 45 miles per shift,” says Henshaw. “So in three shifts, that’s 135 miles per day. We’ve owned three of the Volvo trucks for two years. We don’t calculate their availability, but it’s very good.” (The fourth truck was purchased recently.)
“The plant puts out 570 tons per hour of refuse, so that means each truck hauls about 145 tons per hour,” says Henshaw. At 40 tons per load, that’s about three loads per hour, or a 16-minute cycle time. Occasionally, cycles are reduced to five or ten minutes.
The Volvo trucks typically dump their loads in one place, and bulldozers spread it out in 1-foot lifts. Regulations demand that the material meet a compaction specification. Henshaw says that with 6-wheel drive, the Volvo trucks make a point of driving over virgin fill, where no other truck has tracked. That helps compaction. A roller is only needed during the rainy season, when the fill is wet.
The dam is built up in benches on the side away from the slurry lake. Each bench rises on a 2:1 slope to meet the next bench. At the top, the dam is 80-feet wide. When trucks work the top of the dam they begin by dumping in 1-foot lifts on the downstream side. They work their way upward and over to the lake side of the fill. “When we reach the point that we’re 30-feet wide at the top, then we do our upstream push-out,” says Henshaw. “We push the coarse material out into the slurry pond.”
River View operators like the six-wheel lockup feature on the Volvo trucks. “We lock into 6-wheel drive for just about every load,” says Loyd Patton, who operates one of the Volvo trucks. “If we didn’t have six wheel drive, we would just bog right down in the wet material. Rigid-frame trucks would not perform here; they could not climb the grades. We couldn’t do without the six-wheel lockup.” Engineered ramps at the River View mine are designed at maximum10 percent slopes.