The Gautrain project involved 15.8km underground tunnelling, involving drilling and blasting of tunnels under the city of Johannesburg.

Projects of this magnitude usually take a few years to complete, but the tight deadline of the impending 2010 Soccer World Cup event required an explosives company that could advance at a rapid and efficient rate and optimise blasting cycles.

AEL's Quarry Services division was awarded the tunnelling explosives and initiating systems supply contract against stiff competition, offering two market leading technologies. These included Quickshot / Smartdet Electronic Delay Detonators, which are robust, flexible and user friendly initiating systems and R100G, which is a safe and efficient Underground Pumpable Bulk Emulsion explosive.

The tunnelling route includes 4 stations and 7 emergency shafts varying from 6 to 21m in diameter and depths between 35 to 90m. Considering the majority of the Gautrain stations being situated in close proximity to high value properties such as Sandton and Rosebank, the initiation and blasting system had to minimise air blast and ground vibrations. The blasting was executed with minimal interruption to business and residential areas.

The blasting and tunnelling has been done through two different rock formations, namely Granite and Witwatersrand, a heterogeneous ground composed alternatively of quartzite, siltstone, shales and andesites in various degrees of weathering. To minimise airblast and vibrations, SmartDet, AEL's fully programmable electronic initiating system, was used for the shaft sinking and the QuickShot for the tunnelling.

As part of the contract, the Bombela Consortium required the explosives supplier to manage the strict regulatory and statutory requirements associated with the transportation, handling, storage and usage of explosives in a built up environment.

AEL's Quarry Services Manager, Des Decina says, "Statutory regulation didn't allow for the contractors to store explosives and initiating systems on the various sites. AEL assisted Bombela with sourcing the required permits and voluntarily shouldered the task of handling and transporting the materials from their magazines (storage locations) to the various sites and vice versa”.

“Our technology has really been put to the test," adds Decina. "We were firing rounds of 5.5 metres, compared to the industry average of 3 metres. AEL's high energy bulk emulsion combined with the precision and accurate timing of the Quickshot system allowed for maximum advance rate under challenging conditions and time constraints.”

As the Gautrain's operations have ramped up, Detnet, AEL's sister company, which manufacturers electronic initiating systems, has adapted and customised the product for improved compliance. AEL has also continually trained the customers (users) on the ground to ensure that they are competent and adhere to safety regulations.

Blast advance has been steady with an average weekly advance of 42 metres per tunnel end.

The Marlboro portal and Mushroom Park tunnels, which were developed towards one another, hold the joint record total weekly advance of 128 m.

AEL's proven delivery and support with the Gautrain project has not only profiled its capabilities in blasting services and solutions, but has strategically also affirmed the organisation's position as one of the leading global players capable of delivering reliable and robust electronic initiation technology, within tight deadlines to specific requirements.

EDITORIAL CONTACTS

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