TODAY IN KIMBERLEY’S HISTORY 8 JULY Sorry to say, but nothing today! Ongoing research will surely find something of importance that happened today in Kimberley’s history, but not as yet. Aluta continua. DID YOU KNOW Initially, the various mines were worked by opencast methods. In the early days at Kimberley, the workings of numerous independent claim holders were crowded into the relatively small area of the pipe. As mining took place at greater depths, operations were hampered by many hundreds of independent operators, each running his own aerial rope haulage way. With the increasing depth of excavations, work became steadily more difficult and dangerous. Efficient, large-scale operations became possible on these pipes only when the smallholdings were ultimately amalgamated into one company with the formation of De Beers Consolidated Mines Limited in 1888. Opencast work was abandoned finally in 1890, at which stage some of the mines or “big holes” had reached a depth of about 240 metres. Chambering is the original underground mining method developed in Kimberley around 1890 and successfully used until the mid-1950s. Chambering was essentially a combination of shrinkage stoping and caving, in which advantage was taken of the pressure exerted by loose material accumulated in the open mines. Production was effected by manual loading of ore into coco pans, which were hand-trammed to ore passes. Chambering was superseded by the introduction of block caving which has since been extensively used at the four Kimberley mines. The Block Caving system (see diagram) involves production on a single level by the development of concrete-lined tunnels called scraper drift, side by side at 14-metre intervals across the pipe, beneath a solid block of kimberlite about 180 metres high. From draw points set at five-metre intervals in the sidewalls of the drifts, cones are cut into the still solid block of kimberlite above to a height of 9 metres. The block is then completely undercut by stoping out a slice about 3 metres high, immediately above the cones, causing the solid mass of kimberlite to cave and break up under its own weight. Broken ground is drawn through the draw points into the drifts, where scraper winches remove it to the haulage. The ore is then hauled by electric train to ore passes leading to the underground crushing plant, which reduces the material to 150 millimeters in diameter. It is then conveyed to loading flasks which feed the skips for hoisting to the surface.
Posted on: Tue, 08 Jul 2014 00:06:14 +0000
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