To meet the increased in-house demand of gabbro-based aggregates, Al Jaber has taken delivery of a second Ranger 7002 hydraulic crawler drill fitted with Sandvik T51 drill steels from local distributor Dynatrade, for its Kadra quarry operation, located some 50 km west of Fujairah in the UAE.

The quarry, with a 20-year lease, covers an area of approximately 1.5 km by 750 m in an area boasting one of the region’s toughest rocks. Featuring a density of 2.9 tonnes/cu m, the gabbro is tough, highly abrasive and has up to 50 per cent silica (SiO2) content.
With surrounding hills peaking at around 100 m, Al Jaber is working on a number of faces up to three benches each with varying heights. Drilling is carried out by a Tamrock Ranger 7002 hydraulic crawler drill ordered 12 months earlier, says a Sandvik spokesman.

Ranger 7002
The Ranger 7002 drill features a revolving superstructure fitted with rear-mounted power pack to effectively counter-balance the feed and boom assemblies to provide an inherently more stable drilling platform. The rig also features a TISQ M303 measurement and hole alignment system, which guarantees accurate drilling of production holes.
The turntable mounted articulated boom and drilling module offer a 120-degree arc movement and a large 17 sq m vertical drilling coverage. The configuration provides improved hole positioning range at even the most difficult ground.
A major emphasis has also been placed on operator comfort and safety with the new rig including laminated windows and both FOPS/ROPS protection to the appropriate ISO standard.
Excellent all-round visibility over the drilling area together with logical layout of controls, air-conditioning system, filter air intake and sound proofing to 80 dB(A) provide the operator with an excellent working environment.

Drilling & blasting
Depending on in-house demand for aggregate by the Al Jaber Contracting Company, the quarry generally drills 89 mm diameter holes up to depths of 21 m with 55 to 70 holes per blast. According to P Sudhir, Al Jaber’s blasting engineer, blasts constantly vary according to demand.
He explains: “In total, 44 blasts were carried out in 2005 to meet our own in-house supply of aggregate. We therefore drill and blast to suit demand.”
In 2004 almost 700,000 tonnes of rock was blasted at the Kadra operation. By 2005, in order to meet increased demand for Al Jaber’s construction projects across the UAE, this was increased to more than 1.3 million tonnes.
Illustrating the varying in-house demands for aggregates, figures indicate, for example, a record 145,824 tonnes was blasted in May 2005, whilst March produced a smaller 92,762 tonnes.
As an example of a single blast carried out in 2005 producing 52,488 tonnes provided 18,731 cu m of rock for crushing. A mix of 550 kg base charge/slurry explosive and 5,500 kg Anfo was used for the blast.
“We usually use a 10 per cent mix of booster although this can be as high as 15 per cent where we are experiencing problems with the toe or to provide a cleaner profile avoiding loose boulders,” says Sudhir.
This particular example took 44 holes at 21 m depths and 3 m by 3 m burden and spacing. A further 31 holes were also drilled at 4 m by 4 m pattern to total almost 1,500 drilled metres.
The Kadra quarry comprises predominantly medium hard and hard gabbro. Whilst the Ranger 7002 is currently working in medium hard rock, the gabbro is likely to become harder with increasing depth.
According to Sudhir, drilling in medium hard rock can produce up to 110 drilled-metres over an eight-hour shift when drilling 21-m-deep holes. “As the rock becomes harder however, the number of holes will be less” he says.
The Tamrock rigs with HL700 rock drills are fitted with Sandvik rock tools, including Sandvik Tough T51 3.6 m long MF rods and Sandvik CAPP Black Label 89 mm drill bits.
Such is the abrasiveness of the rock that in the hardest sections Al Jaber is achieving just 300 drill-metres/drill bit. On average, in the medium abrasive rock up to 800 drilled-metres can be achieved.
“We are nevertheless extremely pleased with these figures, achieving better results than expected in this tough and demanding rock type,” says Sudhir.

On-site grinding of drill bits
Al Jaber quarry has been grinding its drill bits since 2004 to ensure maximum drill steel economy, penetration rates and drilling capacity with its Ranger 7002 crawler drills. Holes will be cleaner too and bit service life is doubled.
“The quarry is operating three drill shifts each day – two daytime and one night – six days a week with service, maintenance and washing procedures being undertaken during the free-time afternoon session,” he concludes.
Sandvik is a high-technology, engineering group with advanced products and a world-leading position within selected areas. Worldwide business activities are conducted through representation in 130 countries. The group has 39,000 employees and annual sales of approximately SEK63 billion ($8.74 billion).
The company’s business concept is based on a unique competence in materials technology. This has resulted in a world-leading position in three core areas:
• Cemented-carbide and high-speed steel tools for metalworking applications and blanks and components made of cemented carbide and other hard materials.
• Machinery, equipment and tools for rock-excavation.
• Stainless and high-alloy steels, special metals, resistance materials and process systems.