Investing in a haul road is a great way to protect your valuable asset and deliver exceptional ROI.
However, in both surface and underground mining, badly designed and poorly maintained haul roads, be it primary or secondary, can significantly increase costs.
Not only does one need to factor in aspects such as increased fuel, tyres and other running costs, plus the repair / replacement of major equipment, but there are also long-term and indirect issues such as lost production and safety.
What makes a good haul road and the maintenance thereof?
As a rule, a well mantained haul road allows for a light duty vehicle to comfortably travel at a speed of 60km/h with none or minimal disturbance.
As haul roads start at the loading face and end at the dump, it’s important to:
- Maintain good floor conditions at both ends
- Travel at a reasonable speed in the dump zone
- Establish safe stopping distances, and
- Determine safe sight distances for quicker operator response
Other factors to consider
Smooth constant grades – minimising gear changes, maintaining higher speeds, reducing fuel consumption and spillage.
Optimum road width – 2 truck widths on one-way straights (2.5 on corners); 3.5 truck widths on two-way roads (4 on corners).
Well designed curves and smooth switchbacks – using the largest possible maximum radius and including truck performance/ speed as part of the equation.
Horizontal alignment around curves – incorporating proper width, superelevation (banking), turning radius and sight distances.
Constant crossfalls – maintain minimum slope for drainage, 2% fall if possible (loaded truck on “uphill” side)
Optimal grades – limit to 8 to 10% with minimum (2%) rolling resistance.
Rolling resistance – Increased rolling resistance = increased fuel & tyre costs, increased equipment and maintenance costs, therefore increased cost per tonne.
Specific courses/layers – incorporate sub-grade (0.5m sandy clay), sub-base (1m clean sand), base (1.3m course crushed rock) and surface courses (0.8% fine crushed rock or gravel) dependent on design, size of haul trucks (eg.320t) and material avails.
Safety factors – construct median or collision berms, escape lanes and dedicated roads for smaller vehicles; install appropriate signage.
Road surface roughness – the rougher the surface, the shorter the life of truck components and tyres.
7 things to do to avoid haul road deterioration
- Keep ditches and culverts clear of obstructions and line with rocks/ staked hay bales to minimise erosion
- Do not overload vehicles, thus preventing spillage
- Avoid rutting by using different areas of the haulage lane
- Ensure adequate drainage to cover maximum expected rainfall
- Minimise puddling & refill potholes with good dry material
- Minimise dust problems and maintain compaction with water trucks or sprinklers or proven dust suppressants
- Use graders, dozers, etc to maintain cross slopes, remove spills, and fill and smooth surface depressions.