A unique invention from Adelaide based Broons Hire has been
evaluated at the Leigh Creek Coal Field in an attempt to reduce "haunching" on
the mine haul roads caused by the massive new 236 tonne payload Unit Rig Lectra-Haul
trucks.
Under the direction of Simon Budden, Mining Engineer, initial
investigation revealed that damage to the roads appear to be caused by the
regenerative braking of the trucks when unladen on the return to the bottom of
the open cut, not on their climb to the top when loaded as one would have
suspected.
Maintaining consistent haul truck cycle times is critical to
the mine's effective performance and delays due to a rough running surface,
resulting in slower travel speeds, simply adds to the cost of the extracting the
coal. Maintenance grading, whilst accepted as necessary, is preferably kept to a
minimum and has not always proven successful at eliminating the problem on the
haul roads and approach slopes.
Enter Broons with their 13.8 tonne BH-1300 "Square" Impact
Roller. Drawn at around 12kph by a 250hp 4wd tractor, the Impact Roller imparts
a massive 50kJ with every blow. "Thumping" the surface twice every second it can
cover in excess of 1200m2 per hour with around 20 passes.
The intention was for Broons' Impact Roller to compact the
subgrade of the road formation, reducing the surface movement or "haunching"
beneath the unladen trucks.
The oil shale type brown coal found at Leigh Creek proved
reluctant to absorb moisture to aid with compaction and several procedures were
trialed while the Impact Roller was onsite in an attempt to find the best
solution. These included:
1. Impact Rolling directly onto the surface with no
preparation.
2. Cat 16 Grader to scarify the surface, watering area, then
Impact Rolling.
3. Cat D10 Dozer to deep rip with a single tyne, "flood" the
area with water, then deep rip again before Impact Rolling.
Results indicate method 3 to provide the optimum benefit,
straight away reducing the maintenance grading from twice per day to only once a
week!
Well proven over the last 16 years, the Broons "Square" Impact
Roller has been used at a number of mines throughout Australia and Overseas on
projects including the rectification of failing haul roads, tailings dam and
waste heap construction.
Broons relationship with the Leigh Creek Coalfield goes back
well over 30 years having supplied both a towed Grid Roller and a massive 96T
towed Vibrating Roller to the former owners, ETSA. In addition, Broons provided
a fleet of compaction equipment when the new township, airstrip, retention dam
and coalfield were developed by Adelaide based Tripodi Constructions and
Macmahon Constructions during the late 1970's.
South Australian's still working together!
