WHERE SAFE AND SPEEDY SUPPORT
PAYS OFF

Rock support is often a bottleneck in the business of underground mining and an obvious solution is faster rock bolting. The cost is negligible when compared to the higher profits that can be made by keeping equipment fully and economically employed to increase production.

The mining industry is increasingly recognising that Atlas Copco's Swellex rock bolts, which are quickly and safely installed to give immediate support, are speeding up operations and boosting revenues.

In the tunnelling business, the bolts are already accepted as the key to better operational efficiency. Now they are ensuring higher advance rates, productivity and quicker access to orebodies in mines as well.

In single-face development, high speed rock bolting obviously cuts the time to completion. But in multiple face development or ore extraction, the objective is to utilise manpower and equipment efficiently as well as to advance the faces on schedule. This means that operations must be synchronised so that one does not fall behind, holding up the others and wasting time and money.

The development of Atlas Copco's Rocket Boomer rigs is constantly reducing drilling time - making Swellex the perfect partner to provide reinforcement quickly, so that the next operation can start without delay.

Swellex rock bolts, already renowned in the tunnelling business as the key to better operational economy, are now making their mark in mining as well.

Swellex bolts are now being used to great effect in South African gold mines, where operations often takes place at depths exceeding 3,000 metres. Sinking deep shafts to reach new parts of an orebody involves crippling costs - and
many mines now favour long horizontal tunnels from existing shafts.

Big advances

At the Elandsrand Gold Mine, high-speed development is under way to provide access to the gold-bearing reef through 22 km of tunnels at a depth of 3,100 m.

The mine has dramatically increased advance rates by eliminating the rock bolting part from the drill-and-blast cycle and performing the bolting with Swellex at the same time as the blastholes are drilled.

A railbound Atlas Copco Boomer rig is equipped with two booms and COP 1238 rock drills. The left feed is normal and the right feed is telescopic so that it can drill the Swellex boltholes as well as the blastholes.

Meeting targets

The new Target Gold Mine orebody in South Africa is being accessed by tunnels driven from the existing Lorraine Gold Mine. Initial production from on-reef development started recently, and production from stopes is scheduled for January, 2002.

Estimations put production costs at "well below USD 200 per ounce", the mine life at around 14 years and total gold production at 3.4 million ounces.

There are five crews working on the development. Three of them are using Swellex rock bolts and the other two are installing bolts from another manufacturer. Only the Swellex crews are meeting the development targets.

At the new Target Gold Mine: Atlas Copco South Africa salesman Hedley Birnie (left) with Charles de Villiers, who says he would never want to change from Swellex bolts.

Charles de Villiers is managing one of the Swellex crews, which is using an Atlas Copco Simba 157 rig to drill blastholes and boltholes for the 1.8 m-long Standard Swellex EXL bolts. He says: "I would never want to change from the Swellex bolts. The price of Swellex is rather high - but it's negligible compared to the benefits gained by improving our cycle time and reaching the orebody faster."

Development work could continue for another six years, with the current plan involving 15 levels. The upper level is 2.4 km long and the lowest of the planned levels will be approximately 7 km.

Mining methods

The Neves Corvo Copper Mine in southern Portugal, owned by Somincor, has recently increased annual production from 2.1 to 2.3 million tonnes. Reserves are around 30 million tonnes of copper and 1.9 million tonnes of copper and tin ore.

Mine Superintendent Antonio Salvador says 95% of the ore is being extracted using several mining methods: 60% of the tonnage comes from a modified drift-and-fill method, 20% from benching, 10% from mini-benching, and the remaining 10% from mining of the sill-pillars.

In Portugal: At the Neves Corvo copper mine: From left, Sven Buskqvist, Wirsbo Stålrör AB, Antonio Rodrigues, Somincor, and Torres Marquez, Atlas Copco Portugal.

Drift-and-fill mining is carried out by 13 face-drilling rigs - nine of them Atlas Copco Boomer units. Two more Atlas Copco Boltec rigs for mechanized rock bolting, equipped with the latest Swellex hydraulic pumps, have recently been put into production - and the time taken to install a Swellex bolt in a pre-drilled hole at the mine is now less than 30 seconds.

For benching and mini-benching, the mine is using three drill rigs - two of them Atlas Copco Simba units.

The two fully-mechanized Boltec rigs are installing 2.4 m-long Standard Swellex bolts in the roof and walls of the orebodies, with an average spacing of 1 m. Swellex bolts have been used at the mine for more than 10 years and, in recent years, more than 60,000 have been installed annually.

Says Antonio Salvador: "rock bolting is currently the bottleneck in our production cycle. We have to use several bolting units because the long distances between the different fronts mean greatly reduced utilisation.

"However, we are looking at investing in more units and we will continue using Swellex bolts because of their instant support and easy and fast installation."

Antonio Rodrigues, production chief in one of the orebodies, says: "We have to blast 25 faces per day to meet our production targets, which means time is precious. Although Swellex bolts are more expensive than others, they are the most cost-effective solution for us in terms of the total installation costs.
"And the time we save by using Swellex means more money in our pockets!"

Systematic support

At the Çeltek Coal Mine in Turkey, some 300 km north-east of the capital Ankara, the support system of a gate road has been changed from the traditional steel arches to systematic support with Atlas Copco's Standard Swellex EXL bolts. This follows a joint effort involving Atlas Copco Turkey and a team led by rock support expert Professor Erdal Ünal of the Middle East Technical University. The aim was to introduce the high load-carrying
capacity and yielding characteristics of Swellex to the country's coal industry.

In Turkey: a Swellex bolt is installed to demonstrate its unique ability to provide safe and immediate support.

A universal pull-tester developed by Professor Ünal's team was used to show the superiority of the Swellex bolts in terms of speed, safety and economy.

Time spent on roof support in a cycle decreased from two hours to between 20 and 30 minutes per metre of advance in the gate road, resulting in an increased daily advance rate.

After experiencing the speed and ease of the Swellex bolt installation, the mine management and support crew agreed that the system also offers value for money.

Detailed research

The Ares Gold and Silver Mine is located 275 km north-west of Arequipa, Peru, nearly 5,000 metres above sea level. It is a new ore deposit and the Victoria vein, nearly 2,000 m long and up to 200 m deep, is the main mineralised structure.

In Peru: At the new Victoria deposit in the Ares gold and silver mine: Field testing of different bolts resulted in the choice of Swellex for reinforcement of the five classes of rock at the mine.

The design of drift support in the mine has been the subject of detailed research by the soil mechanics team at the mine and different types of bolts were field tested.

The final choice for both permanent and temporary support in the five different types of rock at the mine was Swellex bolts from Atlas Copco.
Super Swellex and Midi Swellex bolts are being used in areas where the metal content is high and recovery must be around 95% and, in addition, some 1,600 Standard Swellex bolts per month are being installed at the mine.
The mine reports that, thanks to its special features, the Swellex system has not only increased safety but has contributed to an increased advance rate and improved economy.