Haul Road Optimization –
Haul road optimisation takes into account numerous parameters such as functional performance, vehicle operations, maintenance cost models, environmental impacts, and safety factors such as friction and dust. These factors have to be balanced. Haul and access roads on mine sites endure the majority of mining activity and movement therefore are an integral part of the maintenance management system of a haul mine road. A mine haul road is defined according to the class of vehicle using the road. It depends on the wheel and axle load limits of the road design itself. There are three basic types of haul roads. This based on application and specific type of trucks associated are:
- Road legal: Sealed (paved) roads utilized by conventional truck and truck-semi-trailer combinations. Used by single, double or triple trailer road trains, < 120 t capacity
- Road legal: Unpaved roads used by B-double, B-triple and Quad road trains with powered trailer options. They have < 170 t capacity
- Off-road: Unpaved and inpit haul roads for small scale operations and civil construction. Used by articulated dump trucks < 75 t capacity. Custom road trains with > 200 t haulage capacity. High tonnage capacity rear-dump and bottom-dump trucks.
Heavy machinery, high traffic usage and harsh weather conditions mean these roads must be robust, resilient and flexible. GRT’s revolutionary products and processes prevent dust while also controlling soil and surface deterioration. Our products are effective a wide range of soil types, and function so as to keep roads open, improve driving conditions and eliminate potential health threats posed by fugitive dust. The article focuses on evolution, design and maintenance of haul mine roads. It sums up with GRT best industry practice for haul road optimisation.
Evolution of haul mine roads
Mining haul road design has evolved over time. It started with poor road design and maintenance management. It had little asset investment, high haulage costs for fuel and tires. There was always a potential over-spend on road user haulage costs. Shortcomings included risks of damage to trucks and a high fleet impact. Long cycle times, low road uptime and long remobilisation. The mine haul road was not 24×7 trafficable. The interruption due to unplanned maintenance affected production. It has unsafe conditions and unpredictable performance and operation. As technology progressed there was sound design and road maintenance. Complemented with unoptimized total road user costs. The maintenance regime suited to static conditions. Planned road maintenance interventions minimised production disruptions. Reduction to truck damage ensued and improved cycle times. Remobilisation happened quicker with safer and more predictable haul roads. The fourth industrial revolution brought world class road design and management. Asset investment is performance driven to yield return on investment. There is on-going management input and drive. Evident are optimised costs, both from build and operate. This also optimises ongoing total road-user costs perspectives. Maintenance is in real-time to deliver dynamic real-time cost and performance optimisation. Optimises truck and tyre life with low fleet impacts. Haul roads are 24×7 trafficable and safe to operate.
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Mining haul road design
A safe systems approach to mine road design acknowledges humans error is inevitable. The mine haul road system must make allowance to lower severity associated with the risk. A safe system to mine road design requires the following:
- Designing, constructing and maintaining a road system of roads, vehicles and operating requirements. It’s done so that forces on the human body generated in accidents are less than those resulting in fatal injury.
- Improving roads and adjoining areas to reduce the risk of accidents. It’s done to minimise hazards. Haul mine roads design is forgiving. Hence haul roads and roadsides allow a margin of recovery from error.
- Managing speed and speed-related risks on different parts of the road system.
Mining haul road design consists of three components. These are geometrical design, structural design and functional design. Geometrical design integrates design methods with safety audit systems and the mining plan. Structural design utilises CBR, mechanistic-empirical design and layer works. This achieves optimised haul roads. Functional design uses material properties, field and laboratory testing. These benchmark and track functional performance of haul mine roads.
Mining haul road maintenance
Road maintenance happens to restore the road to its original operating specification. This is to conserve the integrity of the road wearing course. It occurs through returning the gravel surface and removing defects. In most cases, this will improve a road and reduce its rolling resistance to 2-2.5%. The sooner the road deteriorates again determines the next maintenance activity. It is important to perform road maintenance with two questions in mind. Where was the maintenance done? What maintenance activity was performed? The first question enables one to understand the road segment of the network. The second questions assesses whether blading, dragging, shallow rip or re-grade took place. It is very important to keep haul road maintenance records of where and what was done. This allows use of historical data to check haul road performance over time. Maintenance reports are cross checked with any other information from the dispatch system. It’s done to confirm the problematic zones. Records of truck speeds, suspension strut pressure spikes, temperature on tyres and operator reports is key. They build a database of useful road maintenance information. The types of haul road maintenance activities: routine maintenance, resurfacing, rehabilitation and betterment.
In practice, many mine roads are poorly maintained due to the lack of road building expertise onsite. Common problems include, dusty surfaces, poor drainage, lack of crossfall, and the absence of compaction in repairs. Understanding how essential it is to build a stable road base so as to keep the routes intact, maintain safety and avoid rising maintenance costs. GRT delivers quality access road dust control and stabilization solutions to keep these vital thoroughfares permanently operational.
Industry best practice
Good haul road practices are key to optimising mine operational costs. GRT’s products and civil engineering expertise can offer the mining industry a service and persepective often missed in the sector. The transit of mined material needs a stable and accessible haul road network. As discussed the layout and planning of haul road is paramount to the success of achieving operational goals. Disruptions should be kept at a minimum. Regular assessment of the state of the haul road is important. The road condition must be free of potholes, ruts and gullies. The passing room must be adequate. High speed operations must have safe corner radii and no debris should be on the haul road. Rubber deposits must be removed on tight rocky turns. The expected road speeds should match the road condition and maintained at all times.
GRTs’ line of highly effective, environmentally safe soil stabilization and dust control products and processes eliminate the need for inefficient watering. Our dust control products also help prevent surface deterioration, potholes and rutting, avoiding haulage downtime, and damage to plant and equipment. Inquire about our industry leading Haul Road Optimization.
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