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