MAINTENANCE
grade for a mine haul road is between 8 and
10% with low rolling resistance of 2% or
less. Travelling downhill laden with a full
load increases the load on the front axle,
generally by the value of the gradient.
A cambered haul road or banked curves
will increase the load carried by the tyres
on one side of the haul vehicle. Most
vehicles are wide and need a lot of space,
both to drive and turn. Anyone that has
ever been stuck behind an abnormal load
transport, would have noted that mining
vehicles may take up the equivalent of
two lanes. Haul roads in quarries should
ideally be three times the width of the
widest haul vehicle, to prevent tyres from
bumping into or scraping along the safety
berms or drop into ditches. The design of
bench and dump areas can increase tyre
life and also reduce transportation spillage.
The turn should be designed to be broad
enough to enable to turn the equipment
quickly without dry steering on loose
material. Dry steering refers to the act of
turning the steering wheel of a vehicle
while it is stationary. This puts strain
on the rack, pinion, pump, tie rods and
bearings. It especially causes undue wear
on the front steer wheels.
Best material to build haul roads
The material used to build the quarry
haul roads should be fines materials
that can be compacted. The fines are
generally derived from waste material
produced either during the crushing and
screening of quarried material, or from
the processing plant where ore is crushed
and milled. Haul roads are built with
various layers and different size material. It
should be ensured that the rock materials
used in the top layer are not over-sized or
sharp. The material should also be packed
down and compacted correctly to prevent
undulations developing. It is therefore
prudent to use a studded compaction
roller prior to using the smooth vibrating
roller to produce the final surface.
The material should not become too
moist when wet, to the extent where
wheels sink into the haul road, bringing the
sidewalls of the tyre in contact with dirt
and wears away the rubber. Lime is usually
added to permanent haul roads to stabilise
clayey or very fine-grained material. If there
is high rolling resistance on the haul road,
the tyres are not biting into the road and in
effect are burning rubber off the tyre.
Environmental considerations
Dust control is also required as part of the
Environmental Management Plan at all
www.equipmentandhire.co.za
The profile of the haul roads, such as length, width, camber and elevation of curves
and gradients has a considerable effect on dynamic overloading and on tyre scrub.
The grade of the road is one of the first features that can be physically felt by the
driver.
The material used to build quarry haul roads should be fines materials that can be
compacted.
MARCH 2020
25