Webinar: Influence of Road Construction on Mining Projects

Roads are the vital connections between different parts of a mine site - horizons, working areas, stockpiles, waste dumps, and processing facilities. The goal is to ensure roads provide the shortest route between two points with consistent optimal slope, minimal switchbacks, and straight alignment. These parameters are often regulated by mining authorities.

When planning in-pit roads, it is essential to consider mine staging. As the pit evolves, roads will need to be relocated, and this process must be managed carefully to maintain access to all pit elements and communications. Road layout has a significant impact on project economics.

K-MINE is a mining software company established in 1994 in Ukraine. By 2024, the company has expanded its reach to Europe, Asia, the United States, and Canada. The team includes developers, surveyors, qualified persons for NI 43-101 and JORC reports, mining engineers, and geologists. K-MINE software covers the entire mining workflow from exploration to production in 12 versatile modules for both open pit and underground mines.

There are three main categories of roads in and around open pit mines.

Internal pit roads are the most critical since they cover the most ground in large pits and require significant attention to design and maintenance. These roads must be wide enough for the largest vehicles to pass through. Auxiliary roads accommodate smaller vehicles. Safety berms are regulated by mining standards and usually overseen by surveyors or geotechnical engineers.

Surface roads connect the pit to other parts of the mining operation - stockpiles, dumps, and processing plants. They are generally wider than internal roads and require a strong rock base to handle heavy dump trucks. Protective barriers such as windrows or visible stakes keep trucks on track.

Dump roads require special reinforcement because dumps are typically made of soft rock. The road base and rolling area need to be reinforced with sturdy materials to support heavy equipment. These roads should be wide enough for the largest transport vehicles, and horizontal inserts are placed on sloped sections to access different dump tiers.

Road pavements for heavy-duty dump trucks fall into two categories: roads on weak or soft base and roads on rocky base. Roads on soft foundations need a thicker layer of rock. Ideally, each layer thickness should be calculated based on the weight of the equipment used in the pit. Layers that are too thin will result in road failure, while overly thick layers lead to unnecessary cost.

Special attention should be given to the top layer, which directly contacts the tires. This layer must meet regulatory standards for parameters like flakiness, angularity, and wear resistance. The final layer can be made from finely dispersed granite screenings cemented with special liquid solutions that fill all voids and strengthen the road surface.

Road maintenance with specialized equipment - graders, bulldozers, and loaders - is essential for keeping roads in good condition.

Roadway width should match the size of the largest dump truck. Roads can be single-lane or double-lane. In tight spaces or when using roundabouts, single-lane roads can work but need clearance pockets every 300 meters. Shoulders act as buffers to ensure safe vehicle passage.

Trenches and drainage are crucial for managing water, which is one of the biggest threats to mining operations. Trench size depends on rock type - wider for soft rocks and narrower for hard ones. Trenches need regular maintenance and should be connected to sumps for effective water removal using a cascade system.

Rock barriers (windrows) can be made from soft or hard rock. The height depends on the vehicles - for heavier vehicles, the barrier is typically half the wheel diameter; for smaller vehicles (up to 40 tons), about one-third of the wheel diameter.

Road slope (gradient) is a major economic factor. A longer road means more distance for transporting rock and increasing haulage cost. However, a slope that is too steep reduces transport speed and efficiency. A transfer slope across the roadway directs water flow into the gutters.

Prism of possible collapse must be considered to ensure no mining elements are placed within the potential collapse zone, which depends on ledge height and the underlying rock properties.

Road profiles depend on location - whether on a dump, single-sided trench, double-sided trench, or embankment. Each type has specific features:

• Roads on embankment require windrows on both sides
• Double-sided trench roads are prone to flooding and need drainage ditches on both sides
• Single-slope profile roads need a trench on one side only
• Standard roads on a ledge have a drainage ditch on the side of the upper ledge and a barrier on the side of the lower ledge

The webinar demonstrates example parameters for roads used by vehicles with a capacity of around 220 tons and a width of about 8 meters, based on best practices from BHP.

Building a road in K-MINE starts with drawing a guideline that serves as a formation guide. This line is then converted into the center line of the road using the "Road Along Center Line" command.

Construction parameters can be dynamically adjusted. Sections where specified radii do not fit are marked in red, prompting the user to change the radius of road curvature or adjust point positions. The "Modify Stations" menu allows elevation changes for each point while tracking compliance with the landscape. All dependent parameters are recalculated automatically.

After confirming the center line, K-MINE generates bend radii, detailed reports, point coordinates, and other information. A road profile is then created using the "Create Line by Cross-Section" command, linking profile vertices to the center line. With a single click, the complete road profile is distributed along the center line.

K-MINE supports automated pit design with and without road integration. Construction begins with determining the pit bottom, creating a list of levels, and calculating the pit contour.

The software can adapt design contours to existing topography. After activating the "Adopt Project to Topography" checkbox, design lines take two forms: solid lines that participate in construction and dashed lines that do not. The "Combine Project and Topography Wireframe" function produces a final project that accounts for topography.

Three project options were compared:

1. Construction from pit bottom without horizontal inserts (reference option)
2. Construction from pit bottom with horizontal inserts
3. Construction from pit top with horizontal inserts

Using K-MINE's block model tools, excavation volumes were calculated for each option by limiting the model between the design frame and actual topography.

Comparing against Option 1 (no horizontal inserts) as the reference:

• Option 2 (bottom-up with horizontal inserts): 12.5% increase in total waste (21 million additional tons), 45% increase in haul distance (1.5 additional kilometers), same ore volume
• Option 3 (top-down with horizontal inserts): 3 million tons less ore recovered, higher stripping ratio, 900 meters additional haul distance

The larger the pit, the more significant these differences become. The number of dump trucks required to support one excavator ranged from 5 to 8, depending on the project option. Each additional dump truck costs over $1 million, plus maintenance, repairs, and equipment replacement.

When a heavy-duty dump truck moves up a slope, the driver cannot see the road section beyond the horizontal insert. This lack of visibility increases the risk of collisions during maneuvers. A constant slope angle provides continuous visual control over the entire road section ahead, significantly reducing accident risk.

Additional negative effects of horizontal inserts:

• Vehicles must constantly switch gears from first to second
• Increased risk of rocks falling from vehicle bodies when transitioning between sections
• Increased cycle time and reduced operational efficiency
• Higher fuel costs and decreased gearbox lifespan
• Reduced average vehicle speed and worsened safety conditions
• More trucks needed to move the same volume, increasing overall project cost

Switchbacks increase haul distance and reduce vehicle productivity because drivers need to slow down to navigate turns. They also introduce potential safety risks and require extra stripping to access the mineral deposit.

Switchbacks are sometimes necessary when the pushback length no longer allows for a straight path. Key design principles:

• Place turning areas on horizontal intersections
• Ensure sufficient radius for the largest dump truck to maneuver without crossing into the oncoming lane
• Maintain straight road sections of at least 30 meters on both sides of intersections
• Avoid crossing more than two roads at a single point
• Avoid Y-shaped intersections that do not meet at right angles

Windrows are crucial for guiding drivers and acting as barriers if a vehicle loses control. Rock barriers are mandatory along the entire length of roads in the pit, on dumps, and on horizontal roads.

On exit ramps and near the lower ledge, windrows must be tall enough to stop a moving dump truck. They can also be used to guide and stop trucks when unloading from dump tiers. Geotechnical engineers should verify that unloading areas are not in the prism of possible collapse.

Windrows should include openings (windows) to allow water drainage to lower elevations. Sometimes pipes are used to direct water flow. Windrows can also serve as bases for power line supports, providing enough clearance for heavy-duty vehicles.

When using large equipment, blind spots become a significant concern. Each type of machinery has specific blind spots that interact differently with other equipment. Heavy vehicles in pits have different sizes of blind spots, and it is crucial to understand how these areas affect visibility.

A common incident type involves personnel parking passenger vehicles in the blind spot of heavy-duty dump trucks. The lesson: always be cautious, mindful of blind spots, and ensure safety before making any maneuvers.

Road surface quality - High-quality road material minimizes tire cuts, increases vehicle speed, and reduces rolling resistance.

Water management - Requires a multi-stage approach: infield dewatering, contour dewatering, and in-pit dewatering. Water significantly affects tire integrity and lifespan.

Ice and fog - Ice turns heavy vehicles into uncontrollable hazards. Reagents can dissolve snow and ice on the road surface. Specialized fog lights on power poles can guide vehicles during fog.

Dust control - Irrigate the top layer and use reagents that absorb fine rock particles.

Potholes and humps - Must be addressed promptly. Humps should be cut with a bulldozer; potholes filled with small crushed stone or gravel.

Falling rock from vehicle bodies - Must be reported to the shift engineer and removed promptly.

Transport berm collapse - Widen the road by moving the side or implement traffic control signs and priority passage ru