Tag Archives: SME Annual Conference & Expo

Barrick cuts waste, boosts reserves from modified bench steepening at Goldstrike

An alternative method of steeping the open-pit benchface at Barrick Gold’s Goldstrike mine in Nevada, US, has shown significant net benefits through a reduction in mined waste tonnes and an increase in gold reserves, according to a paper to be presented at the SME Annual Conference & Expo on Monday.

The paper, Steepening Of Inter-ramp Slopes On A Final Wall At The Goldstrike Open Pit, will be presented by Barrick Nevada’s Chief Geotechnical Engineer, Jeff Mattern.

Located on the Carlin Trend gold belt in north-eastern Nevada, the mine has produced over 43 Moz of gold during the past 30 years.  Mining at the Goldstrike open pit has seen its share of slope instabilities, according to Mattern. “In areas where slopes have remained stable, consideration has been made for potential slope steepening of final walls,” he said.

Looking to potentially employ steeper slopes for significant economic benefits, Barrick has taken the commonly used Modified Ritchie Criteria for catch bench width and adjusted it, “resulting in quantified, rock-specific formulas for bench width and rock fall berm placement”, Mattern said.

“The result is an interramp slope angle increase of 2° on a 300 m high slope, without the necessary purchases and procedural changes that would be required for pre-split drilling and blasting,” Mattern said. This occurs in Vinini, Rodeo Creek and Popovich rocks with benches 12 m in height.

The employment of this method has shown “significant” net benefits through a reduction in mined waste tonnes and an increase in gold reserves, he added. In fact, this exercise in a single layback, saw waste stripping decrease by around 9 Mt, while 35,000 oz of gold has been added to mine reserves.

Mattern concluded: “Ongoing monitoring of slope performance, slope design compliance, optimisation of operational practices, and collection of detailed geologic data can all help to provide the right information for potentially steeper slopes and significant economic benefit.”

Drum motors for extreme operating environments come under the SME spotlight

Alexander Kanaris, President of Van der Graaf, will put forward the benefits of using the company’s GrizzlyDrive™ drum motor with IronGrip lagging in extreme environments at the SME Annual Conference and Expo on Monday.

In an abstract ahead of the conference, Kanaris said: “Conveyors powered by external motors and gearboxes, along with v-belts, chains, couplings and pillow block bearings, often operate with relatively low efficiency and require regular maintenance.

“With rising electrical and labour costs, mining and aggregate industries are forced to evaluate ways to minimise downtime, reduce maintenance costs, increase worker safety and ultimately increase profits.”

According to Kanaris, new drum motor technology has addressed efficiency and operator safety concerns. An internally driven conveyor drive, the drum motor “eliminates external components, houses the electric motor and gearbox inside the drum, increases operator safety, saving space, eliminates scheduled maintenance, increases longevity and overall efficiency”, Kanaris said.

“With v-belts, chains and couplings no longer required, the internal drive design drum motor, has efficiency gains of up to 30% and lower operating costs,” he said.

“Reliability and longevity of conveyor drives pose challenges for belt conveyors to operate in harsh and abrasive environments and failure is ground zero for loss of production. The latest Van der Graaf GrizzlyDrive drum motor with IronGrip lagging is developed specifically to operate in these extreme environments.”

The GrizzlyDrive is available from 3-50 horsepower and 8.5″ to 42″ diameter, with thepatented IronGrip high performance lagging design engineered for harsh and vibratory applications, according to Van der Graaf.

Battling convergence events at BHP’s Broadmeadow coal mine

Following a number of “severe convergence events” after employing the top coal caving method at the Broadmeadow coal mine in Queensland, Australia, in 2010, BHP and SCT Operations Pty have put in place a geotechnical monitoring programme to mitigate these issues during the operation of the latest longwall mine.

In a paper titled, Management of Initial Convergence Events at Broadmeadow Mine, R Coutts, K Mills, D Lynch and M Martin; BHP, Moranbah, Queensland, Australia and SCT Operations Pty Ltd, Wollongong, New South Wales, Australia, will discuss these practices at the SME Annual Conference & Expo on Monday.

“The mine introduced a top coal caving (TCC) longwall (LW) face in 2010, but since then experienced a series of severe convergence events soon after starting each panel,” the authors said in a presentation abstract. “During LW8, LW9 and LW10, weighting events occurred at 60-70 m retreat resulting in equipment damage and the longwall almost becoming iron bound.”

The authors said considerable effort was required in LW10 to regain sufficient clearance for operations to resume, with LW11 characterised to have a similar risk of a weighting event to LW10.

The authors said: “This presentation documents the learnings from a geotechnical monitoring programme undertaken during LW11 and details the operational methods used to mitigate these initial convergence events. It also comments on the significance of the top coal caving technique to the convergence events.”

BHP commented in its recently released half-year results to end-December, that coal volumes were up compared with the same period a year ago; a period when Broadmeadow’s output was affected by roof conditions.

Broadmeadow is owned by the BHP Mitsubishi Alliance joint venture, which owned 50:50 by BHP and Mitsubishi.

When the top coal caving method was initially employed at Broadmeadow it was the company’s first mine in Queensland to use it. Employing this method was expected to lift recoveries from around 60% to 90% in the Goonyella Middle Seam and increase production rates, it said in a 2013 briefing.