The importance of correct haul road design

A lot of careful planning and engineering needs to go into designing haul roads in order to guarantee fast wet weather recovery. Haul roads should be built on an angle of between 1% - 4% so that water sheds off the road and the road is less affected by rain. Water that sheds off the roads can go straight into strategically located drains. This helps roads to dry out in a matter of hours instead of days. 

Proper haul road design also mitigates the need to send out graders or dozers to cut the mud off the road to a level where it’s not so wet anymore. In cases of poorly constructed roads, constant cutting is often performed to try to get the trucks back out in operation. 

However, repeated cutting creates further issues as eventually there will be no compacted material left underneath. And if the rain starts again, the road is just going to become soaked and muddy once more as it’s just been graded and opened up. This approach is really just a vicious cycle which ultimately leads to the destruction of roads. 

Stabilising haul roads with bitumen emulsion 

Designing haul roads with sufficient drainage is just one aspect to reducing downtime from heavy rain and improving overall productivity in coal mines.

Stabilisation of haul roads during the establishment phase provides a significantly improved and smoother running surface. This process will reduce the need to regularly grade and re-sheet roads. It will further improve the rolling resistance for mobile equipment and thus improve cycle time efficiency.

Haul roads can be stabilised by incorporating a bitumen emulsion product into the wearing course layer of the haul road to bind loose material. This also provides a surface seal that significantly reduces wheel-generated dust and the ingress of water into the road-base.

Whilst this process of incorporating bitumen during the establishment phase can be seen to be expensive, it has been proven to add value in the long run. 

First off, less road watering is needed for dust control purposes due to the reduction in wheel-generated dust. This lowers water usage costs dramatically which is particularly advantageous during periods of drought. 

Furthermore, with improved visibility due to less airborne dust, haul truck drivers can confidently travel at faster speeds, let’s say 60km/hr on average rather than 20km/hr. This allows coal mines to increase daily tonnage which quickly justifies the initial road establishment costs.

One final benefit of stabilising haul roads with a bitumen product is that because the surface is so much smoother, coal mines experience much lower tyre maintenance and fuel costs. Roads which are constantly muddy and riddled with potholes lead to much faster tyre wear and more accidental cuts. Similarly, roads which are rough to travel across burn much more fuel due to drivers having to constantly stop and start. 

All in all, haul roads which are stabilised with bitumen products cost coal mines less in the long run. Smooth roads make for smooth truck cycles and increased profits for the mine.