Modern Quarrying October-November 2016

TECHNICAL FOCUS HAULROADS

Invariably, mine management wishes to know how to benchmark the haulroad network, and the effectiveness of the existing materials. A procedure was devel- oped to relate a range of defects to pro- vide a defect score (Thompson and Visser, 2000a). Defects are evaluated according to the severity of each defect and the areal extent of occurrence to provide a sump of all the defect products as a defect score. The defect score can be related to the need for maintenance, as it was devel- oped in conjunction with mine mainte- nance teams. Figure 5 shows the influence of daily traffic (in kilotons) and the effect of a substandard wearing course material compared with the correct material. The maximum defect score on the mine was 60, which dictated the maintenance fre- quency. Interestingly, Komatsu adopted this procedure and trained their field staff to provide the mine with recommenda- tions regarding haulroad quality and how to improve productivity, reduce costs, and get the best service out of the trucks.

• Freedom from excessive slipperiness in wet weather. • Low cost and ease of maintenance. By examining what wearing course mate- rial properties lead to defects, a specifi- cation has been developed for wearing course materials selection as shown in Figure 4 . The guidelines are based on an assessment of wearing course material shrinkage product (Sp) and grading coef- ficient (Gc), defined as:

Figure 5: Predicted improvement in functionality for new wearing course material mix at 5,0 and 45 kt/day traffic volumes (Thompson and Visser, 2002).

( P 265 – P 2) x P 475 100

Sp = LS x P 425 Gc =

Use of the correct wearing course mate- rial resulted in a significant improvement in the times between blading, from 3,5 days for the poor-wearing course to seven and 10 days for the improved wearing course material on roads carry- ing 45 and 5,0 kt respectively. Besides determining the defect score, the visual inspection of defects was also correlated to rolling resistance by considering defects such as potholes, corrugations, rutting, loose material and stoniness in

Where: LS

= bar linear shrinkage P 425 = percentage wearing course sample passing 0,425 mm sieve P 265 = percentage wearing course sample passing 26,5 mm sieve P 2 = percentage wearing course sample passing 2,0 mm sieve P 475 = percentage wearing course sample passing 4,75 mm sieve

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