# A New Method for Haul Road Design in Open-Pit Mines to Support Efficient Truck Haulage Operations
## 4 Case Study
### Creation of Input Data  
Assuming that the gold ore body is to be developed as an open-pit mine, the optimum boundary of the open-pit mine was analyzed by applying the Lerchs-Grossmann algorithm, which is a representative boundary optimization algorithm for open-pit mines (see Figure 11a). Table 2 lists the factors and costs considered when calculating the economic values of all blocks comprising the gold ore body. The optimum boundary was analyzed as the connection of two mines. In addition, due to the shape of the ore body, a small mine was formed with a large vertical width in the N-S direction and a small horizontal width in the E-W direction. The maximum depths of Pit 1 and Pit 2 are 156 m and 96 m, respectively, and the overall slope of the mine is 45\({}^{\circ}\) (100%). The bench inside the mine was designed by using the analysis result obtained for the optimum boundary of the mine. According to the mine design guide, the bench width was designed as 7.5 m, the bench height as 15 m, and the bench face angle as 63.4\({}^{\circ}\) (approximately 200%) (see Figure 11b). \begin{table}
\begin{tabular}{c c} \hline \hline
**Economic Parameters** & **Value** \\ \hline Price of gold (\$/ounce) & 1300 \\ Recovery (\%) & 90 \\ Mining cost (\$/tune) & 2.5 \\ Selling cost (\$/ounce) & 35 \\ Processing cost (\$/ounce) & 18 \\ Revenue factor & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Economic parameters and values for calculating the economic value of a block. Figure 11: Result of the open-pit boundary analysis. **(a)** Optimum boundary showing the lower and upper zones (denoted Pit 1 and Pit 2); **(b)** Result of designing the bench, waste dump, and stockpile. In addition, the design located a stockpile on the eastern side of the mine to store the ore moved by trucks and a waste dump to the northwestern side of the mine. The bench design result was converted to a DEM with a 5-m resolution (see Figure 12a). Two departure points were selected for the trucks: the working areas at the bottom of Pit 1 and Pit 2. Furthermore, two destinations were selected for the trucks: the respective entrances to the stockpile and the waste dump. The cost map was calculated by considering the time the dump trucks required to travel 1 m. We calculated the truck travel time by using the approximate change in the travel speed of a truck for the haul road slope in a large open-pit mine reported by [PERSON] et al. (2012) (Table 3). When the bench and haul road are constructed, the ground surface is excavated first based on the mine design results. Thus, the terrain slope was assumed as 0% (0\({}^{\circ}\)) and the truck speed as 25 km/h in the initial excavation step of the haul road. Therefore, the cost of all terrains was calculated as 0.14 s/m. When setting the road slope limit, the local characteristics of the mine and the gross vehicle weight used in the mine should be considered ([PERSON] et al., 2013). The gold mine excavated in the study area is a small mine, the horizontal width of which is not large. Due to the local characteristics of the mine, a haul road with a relatively high slope should be designed to interconnect the bottom work site of the mine and the waste dump or the stockpile. Figure 12: Input data set for least-cost path analysis. (**a**) Digital elevation model of the study area (resolution = 5 m). (**b**) Vertical factor graph. (**c**) Horizontal factor graph. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Haul Type** & **Grade (\%)** & **Approximate Speed (km/h)** \\ \hline \multirow{3}{*}{Full haul moving uphill} & 0–4 (\(\approx\)0\({}^{\circ}\)-2\({}^{\circ}\)) & 25 \\  & 4–8 (\(\approx\)2\({}^{\circ}\)-5\({}^{\circ}\)) & 20 \\  & 8–12 (\(\approx\)5\({}^{\circ}\)–7\({}^{\circ}\)) & 15 \\  & over 12 (\(\approx\)over 7\({}^{\circ}\)) & 10 \\ \hline \multirow{2}{*}{Empty haul moving downhill} & 0–4 (\(\approx\)0\({}^{\circ}\)-2\({}^{\circ}\)) & 25 \\  & over 4 (\(\approx\)over 2\({}^{\circ}\)) & 40 \\ \hline \hline \end{tabular}
\end{table}