Surface haul road resilience
In surface mining, the transportation of ore and waste can account up to 50-60% of the operating costs. Given the pivotal role of haulage in many mining operations, even small improvements in haul road performance have significant potential to reduce costs. However, there are very few tools available to site staff with which to model and evaluate the cost and practicality of haul road improvement campaigns against the benefits from reduced rolling resistance, cost of haulage, cycle times, improved trafficability and resilience of the alternatives.
Current haul road design, build and management methodologies, although well-developed, are poorly adapted to the requirements of current and especially future operational optimisation challenges.
The overall approach to this project – ‘Improving the resilience of surface mine haul roads’, was to develop cost effective, 24/7 roading practice and engineering controls, including haul road material selection, design and construction practice, road maintenance management and circuit prioritisation for minimised rolling resistance (RR). Critical in the approach was recognition and assessment of sheeting material options in terms of dry-and wet-weather resilience and trafficability (RR). Wet-weather often has an associated haulage downtime, both as a result of trafficability limitations and re-mobilisation delays, in addition to the inherent deterioration which requires regular road maintenance interventions. The sustainable economics of any haul road intervention – routine (grader) maintenance, resheeting or even rebuilds – needs to be assessed in terms of the value any such investment generates, from improved haulage efficiencies.
The research approach was based on a two-phase approach;
- To assess current practice and haul road trafficability from site production and test data and correlate this with materials, design and construction practice limitations.
- Revised specifications and tools were developed to assist industry in recognising current trafficability issues and how they translate into an opportunity for haul road improvement.
Some of the technology innovations developed as part of this work include;
- A more reliable approach to estimating likely resheet requirements for mine roads, based on future planning scenarios and planning data, with the ability to predict when a haul road resheet is required.
- A trafficability assessment and maintenance prioritisation methodology,
- So that site staff can conduct audits of road performance on a consistent and comparable basis. The methodology is well-suited to an app platform and since it uses actual site road ‘defects’ as prompts in the analysis, is a useful training tool for staff involved with road maintenance and haulage management.
- Also reports a rolling resistance estimate based on road condition. This can be used to compare various segments of a network of roads to determine the extent of deterioration, and more critically, the benefit that would be derived from a maintenance intervention.
- Maintenance management protocols, coupled to revised operational guidelines, enable operators to quickly assess the value add of routine road maintenance, or assess in the longer term, the benefits from a resheet of their roads and critically, the value any such investment generates, from improved haulage efficiencies.
The concepts developed in this work have been mapped to the existing state of knowledge of underground roadway design. With underground bulk and autonomous mining becoming a mining method of choice into the future, our current roadway design and build methodologies are not fit-for-purpose and are poorly adapted to the requirements of current and future operations.
The economic case is similar to surface roads – a significant cost and productivity penalty associated with poor roadway design and materials. The goal of this new research effort is to develop a roadway predictive design model and process solution that can be applied globally, with minimal site and material constraints, to provide short build-time, low-cost, low-maintenance, high-performance underground roadways to suit the requirements of high productivity – high capacity and autonomous (conventional and battery-electric) materials handling systems.