MINING bauxite is not like typical open-pit operations - the ore is shallow and covered by overburden containing impurities that affect refining. After the overburden and secondary overburden are removed, what’s left is an uneven surface that has to be levelled so equipment can access the site.
|The Vermeer T1255III Terrain Leveler® provides greater operational efficiency in bauxite mining operations.|
As for the actual mining, up to 90% of work is on hills or contours while ore is distributed over different areas with different grades, meaning that bauxite crews have to mine out of several pits simultaneously as opposed to a conventional open pit mine.
The mining itself has a unique set of challenges, including the uneven surface present after the caprock is exposed – it is undulating, almost desolate and largely inaccessible with earthmoving equipment. Even dozers and track vehicles cannot traverse it. To provide mining machines access to the caprock, mined bauxite is hauled in, placed on the edge of the site and pushed into the gaps by dozers or loaders.
Backfilling is not simple. A substantial amount of material must be hauled in to fill the gaps, which requires a collection of equipment, including haul trucks, dozers, scrapers and wheel loaders, and takes time, man-hours and money. It also requires construction of a development road to get backfill material to the site.
The material used as backfill must be handled twice. First, the bauxite is hauled in from another part of the mine and spread over the area. It then becomes mixed with existing ore in the pit after the caprock is blasted and is mined again.
An Australian bauxite mine has taken an innovative approach to this problem by purchasing a T1255III Terrain Leveler® surface excavation machine (SEM) from Vermeer. The machine breaks up the caprock, eliminating the need for backfill material. The mine estimates that the Terrain Leveler SEM reduces the time it takes to complete this process by more than 50%.
The Terrain Leveler SEM can cut a swath up to 68.6cm deep and 3.7 metres wide in a single pass and operates with a top-down cutting motion developed by Vermeer, allowing the cutter teeth to penetrate without using the machine’s tractive effort to drive teeth into the rock. As the unit travels the drum rotates and the teeth on top advance over the top of the unbroken material surface, promoting greater operational efficiency as more horsepower goes into cutting rock and less into moving the machine.