Mixed news at San Jose

Production and Markets

The drilling of a 38cm pilot hole had reached a depth of 25m by the end of Wednesday in the attempt to rescue 33 miners trapped underground since August 5 at the San Jose copper-gold mine in Chile.

A large-diameter Strata 950 raise-boring machine (transferred from Codelco's Andina mine) is being used by local mining-contractors working for South Africa's Murray & Roberts group (M&R).

The powerful Strata 950 (one of only six in existence) was designed in Kalgoorlie by Australia's RUC Cementation Mining Contractors Ltd (part of the M&R group) for underground-to-underground raise-boring of holes up to 6m in diameter over a length of up to 1,000m.

The machine first drills a downward pilot hole and then either reams a wider hole from below (at a maximum rate of 40m/day) or downwards (this 'blind' reaming is much slower, at 20-25m/day). The final diameter in this instance will be 72cm to allow the use of a 65cm 'escape module'.

The 702m pilot hole is expected to take four weeks to complete. By then the Cementation group will have made a decision whether it is possible to use the more efficient raise boring method, or proceed, as planned at the moment, with blind reaming.

Worryingly for the rescue attempt, Mining Journal has no record of full-width blind reaming ever before being conducted at lengths in excess of 250m. Raise boring, however, will require the reaming head to be attached underground.

Sources on site say that Baker Hughes Mining Tools, part of the Atlas Copco group, is researching whether the unit can be broken into parts for lowering down the pilot hole for reassembly by the trapped miners.

Meanwhile, the operating company, Cia Minera San Esteban Primera SA, is reported to have submitted a document before a local court requesting a creditors meeting in order to consider a possible bankruptcy filing.

More information in this week's Mining Journal.