Drill rigs and rock tools from Sandvik Mining and Construction of Sweden have helped get a major highway project in Qatar back on track.

The three drill rigs and rock tools from Sandvik have helped increase productivity  by 50 per cent on the 40-km-long Dukhan Highway project, making up for earlier delays experienced due to pockets of coral limestone that were harder than forecast.
The Gamuda-WCT joint venture project- comprising two of Malaysia’s leading civil engineering contractors – is working on the $206 million western section of the ‘chisel and excavate’ mega road project.
Originally built 18 years ago, the two-lane highway is being upgraded to a dual four-lane highway to provide improved access for the development of Dukhan Industrial area, as the region expands as a petrochemicals and gas hub.
The western section extends from the town of Al Shamaniyah to Nasarit on the outskirts of Dukhan, located some 80 km west of Doha. The new highway award forms part of a proposed major road system providing access to the long-awaited causeway to Bahrain, the Salwan Road to Saudi Arabia and the new North Road.
An 800-m-wide corridor is being cleared across the existing two-lane highway to prepare access for the dual four lanes and ensure room for future expansion. Each of four lanes has a total width of 14.6 m with a 3 m paved shoulder plus a 1 m hard standing. The contract also includes five interchanges, six camel underpasses plus camel fences on both sides of the new highway.
The highway’s route crosses a terrain of fragmented coral limestone with pockets of particularly hard limestone with a density of 2.8 gm per cu cm – described by the JV plant supervisor Eddie Mansfield, as “hard as shell”.
With approval for blasting difficult to obtain in Qatar, the joint venture – in common with other contractors on similar projects – had opted to use hydraulic hammers to ‘chisel’ the limestone; relying on a fleet of more than 100 hammers – 50 owned by the JV project and 55 rental, fitted onto 20 to 30-tonne-class excavators.
But in some areas, it was found that the hammers made little impact on the pockets of hard limestone causing the project to fall behind its 23-month completion schedule.
The joint venture then opted to buy in a fleet of six hydraulic drill rigs including three Sandvik Tamrock rigs – a Ranger 700 Rock Pilot, a Ranger 700 and a CHA 700. All six rigs have been fitted with Sandvik rock tools including T51 drill rods and 102 mm ballistic button Retrak drill bits.
Delivered at the end of October 2005, the three Sandvik drills made an immediate impact increasing productivity by around 50 per cent, says Martin Lindfors, spokesperson for Sandvik.
All three rigs are hydraulic self-propelled surface models equipped with a rod handling system. They are self-contained units providing fast progress with high power and offer precision drilling and versatility, he adds.
The Ranger 700 Rock Pilot features a Caterpillar diesel engine and gearbox power-pack, which divides the power for hydraulic pumps and flushing air compressors. The power-pack is mounted crosswise at the rear of the rig to ensure a counterweight on the opposite side of the boom and feed, regardless of the drilling direction.
“One of the major advantages of the Ranger is its high suction-capacity dust collection system, which makes it perfect for working in an urban environment. The machine complies with the local health and safety and environmental regulations and also with the labour regulations, with its roll-over-protected, wide-visibility operator’s cabin,” says Lindfors.
He continues: “The Rock Pilot drilling system adjusts the rigs drilling power automatically, reacting to changing rock conditions and sending the optimal amount of power to the rig’s drilling rods. Implementing a 300 mm by 300 mm drill pattern, up to 200 holes are drilled per shift to a depth of 3 m. The hammers then loosen the limestone using the 102 mm-diameter drilled holes. Using this technique means that 75 per cent of the rig’s engine power is being used for drilling power compared with typically 50 per cent. The rigs are therefore providing virtual non-stop drilling power – often just swinging the boom for each hole.
“As a direct result, the JV is achieving approximately 6,000 drilled metres per drill bit without regrinding. The project contractors experienced a hard pocket of limestone to a depth of 3 m over the first of six camel underpasses, which was 100 m by 15 m-wide. In these hard pockets, the rig operator was still able to drill each 3 m deep hole in less than 3 minutes using the Sandvik rock drill bit. Approximately 5 million cu m of limestone will be excavated along the two 40-km sections, with the JV reusing approximately 3 million cu m as infill. Additionally, 0.5 million cu m will be used for sub-grade and approximately 1.2 million cu m for the sub-base. Aggregates will be imported for asphalt production to meet QCS specifications.
The highway construction will feature a 500 mm sub-grade, a 200 mm sub-base and 330 mm asphalt.
“We are confident of making up the delays in excavation caused by the harder rock conditions than forecast with the delivery of the three Sandvik Tamrock rigs,” says John Reynolds, project manager. “Three lanes over 10 km have already been asphalted and approximately 25 km sub-grade laid by mid-January this year, and with a completion date of August 2008, around 65 km still remain to be drilled and chiselled,” he adds.