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with the design and initial construction of the road. In haul road construction, the tradi- tional method is to import material to the road site. Due to the scale of mining operations, the size of the material is often larger than is desirable. Miedecke often sees oversized material in the crit- ical 2-m-deep (6.5 ft) layer below the surface, which will lead to inconsistent compaction and settlement that in turn results in high maintenance and grading costs after construction. "You've got very poor particle size distribution, which leads to voids among all those rocks," he said. "The mining company will continue building the road over that area, but as time goes on, there will be settlement and differential compaction, and then the road becomes undulated and difficult to ride, difficult to grade. It can lose drainage integrity. You'll have ponds in low areas of the road. "It becomes a compounding problem." A fleet of equipment is necessary in this traditional approach, including shovels or wheel loaders and haul trucks to move material to the road con- struction site, one or two large bulldoz- ers, one or two large graders, a water cart, and a compactor. There are a lot of steps in this approach. In fact, Proof Engineers has an 11-action process just for the pro- duction of surface material. Once a road is complete, main- tenance is a major ongoing issue. Dealing with water—drainage—is the top priority. "Water will destroy your substruc- ture of the road if it's in the wrong places," Miedecke said. Another maintenance item in both hard rock and coal environments is spillage from trucks. A lot of fine mate- rial falls out of trucks and gets run over. When it gets wet, it can become slip- pery. And then the mine loses time due to wet weather. Also a factor is the growing size of haul trucks and their payloads. There are now ultra-class trucks with gross weights of 650 metric tons (716.5 tons), or more. The pitch and yaw char- acteristics of the large trucks put more stress on the road as a whole and deep- er into the substructure. Miedecke has seen trucks essentially dig up material from 3 or 4 m (9.8 or 13.1 ft) below the surface of seemingly well-constructed haul roads. He recalls an instance a couple of years ago when a haul road in Australia that had been preforming well DECEMBER 2015 • E&MJ; 47 www.e-mj.com H A U L R O A D S Once a road is complete, maintenance is a major ongoing issue. Dealing with water—drainage—is the top priority. Because it produces an acceptable final particle size on its own, a surface excavation machine eliminates sever- al steps normally needed to produce adequate road construction material, including drill and blast, crushing and stockpiling, and the hauling of in situ material for processing.