WINNING
All photos by Nicola Theunissen
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.
level and square on the tyres, decreasing side forces on the tyre casing, and reducing scuffing and wear on the treads and allows trucks to operate at more consistent speeds, which means less braking and less heat.
Grade is also important because it affects where the load sits on the tyres. The ideal load distribution is for 33 % of the load to be in the front of the truck and 66 % in the rear. The ideal grade for a quarry haul road is between 8 and 10 % degrees, 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 machine.
Haul roads in quarries should ideally be three times the width of the widest truck, so tyres do not bump into the safety berms or drop into ditches. The design of bench and dump areas can increase tyre life and reduce spillage. The turn should be broad enough to enable to turn the equipment quickly without dry steering on loose material.
In addition, the material used to build the quarry haul roads should be fine materials that can be easily compacted. Haul roads are built in various layers by using a range of different size material. It should be ensured that the rock materials used are not oversized or sharp. The material should also be packed down and compacted correctly
Equipment and tyres used in a quarrying operation must be robust enough to withstand tough conditions.
16 _ QUARRY SA | MAY / JUNE 2018