Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/387031
Design and Maintain Good Haul Roads OPERAT H aul roads are the lifeline of a quarry, providing a safe route for materials to be transported from one place to another, mainly between the pit and the crusher or processing plant. e shorter the haul road, the faster the truck cycle time, but the local terrain may require a longer road in order to make it safe for travel. e ideal haul road should be smooth and free from potholes, ruts, and washouts. e grade should be smooth and constant with plenty of room for vehicles to pass each other. Corners should allow trucks and other vehicles to operate safely and reliably at optimum speed. All these things should be considered during the design phase of the pit. Many factors can aff ect the place- ment and design of haul roads, including climate, environmental conditions, and the local geology, as well as the size of the haul trucks that will be operating on them. In rainy climates, drainage ditches can keep haul roads from washing out, causing delays in cycle times. Geo- logic conditions, such as cracks and faults in the highwall, can determine how close a haul road can come to the highwall or edge without becom- ing a safety concern. ese things should all be considered during the design phase, but a erwards as well. "Sometimes, we place haul roads in slightly diff erent locations," says Bryan Smith, mine development and blasting manager at Luck Stone. "When we get down to a certain bench or portion of the pit where we want to place a haul road and realize we have some unfavorable geology, we have to make some changes to make sure the haul road location is safe." Close a ention should be paid to turns and crests in the roads. Opera- tors need a good line of sight in order to avoid hazards without having to slow down. Super-elevated curves are important, especially in switchback areas. A good super-elevated curve will allow haul trucks to maintain their downhill speed throughout the curve without having to apply the brakes, thus reducing brake wear and extending the life of the tire. "Advance the time and the money up front to design and build the cor- rect haul roads," says Kent Cli on, senior market professional – Mining Equipment Application at Caterpil- lar, Inc. "A er you start running trucks on the road, it's hard to go back and do a redesign. And once you've gone through the steps of de- signing a good haul road, and you've used good material to construct it, you need to maintain that haul road to the design standards you had when it was built." AGGREGATES MANAGER Haul roads should be designed wide enough for two haul trucks to pass each other safely. On one-way haul roads, the recommended width is two to two and a half truck widths. On two-way haul roads, a minimum of three to three and a half truck widths is recom- mended on straightaways and a minimum of three and a half to four truck widths for curves and corners. The haul road width should also allow for berms and drainage. A slight 2- to 3-percent crossfall helps with drainage. Once the haul road is designed and constructed, maintenance is a must. Any washouts or pot holes should be repaired im- mediately, and the road should be kept as smooth as possible. A good way to test haul roads for smoothness is to take a light vehicle out to the pit and run the road. If it's extremely rough in the light vehicle, it's having the same effect on the mining equipment. 1 Allow space for trucks to pass 4 Haul road maintenance is a must