The D-Bolt is grouted only at its paddle-shaped anchor points, leaving the smooth sections to freely deform.

According to DRS executives, the company's main focus has been on providing reliable technology that ensures safety and provides cost savings for underground mines, particularly where challenging ground conditions involve squeezing or dynamic risk management. DRS has developed the D-Bolt, a novel rock bolt specifically designed for rock reinforcement in squeezing and burstprone strata.

DRS will be integrated into Normet’s Rock Reinforcement business line. Mike Rispin, senior vice president of Normet Group, said, “Focus will be maintained on bringing the innovative technology of the D-Bolt to our existing and new customers. Blended with our expertise in resin- and cementitious-based bolt grouts, and coupled with a proven track record in rock mass reinforcement via injection, we offer an unparalleled array of solution offerings.”

“This acquisition is a good strategic fit to Normet as it broadens our offering to underground customers and reinforces our aim to be a total solution provider especially in ground support and rock reinforcement,” Tom Melbye, president of Normet Group, said. “With the D-Bolt system, together with our sprayed concrete, grouting and injection technologies and products, we can now help our customers make underground mines and tunnels safer, even in difficult strata and high stresses and deformations.”

Normet said following successful laboratory and field tests, that began in 2008, and the start of commercial sales in 2010, DRS has gained a strong market share of rock support business, particularly in the Nordic region, Canada and Australia. A recent presentation by a company representative indicated that the D-Bolt was in use, being evaluated, or receiving interest from a number of operators. According to the presentation, it is currently in use to control rock-burst conditions at LKAB in Sweden, used in “squeezing-ground” conditions at Boliden and at three Canadian mines for squeezing and/or seismic conditions. It also is being tested at six other Canadian mines, at a large mine in Chile, and has been involved in ongoing evaluation from BHP Billiton in Australia.

The bolt itself comprises a smooth steel bar with several oval-shaped, double-paddle-type “anchor” points along its length. The bolt is grouted, or fixed, only at the anchor points, leaving the smooth sections between the anchors to freely deform. The bar, according to DRS, is manufactured from special steel with enhanced mechanical properties that provide high strength and ductility. D-Bolts are available in 22.2 and 20.5 mm diameters, in lengths from 1.8 to 3.2 m, and with M24 threads for the larger diameter bolts and 7/8 in. UNC threads are used for the smaller diameter version.

“We believe that Normet, which shares DRS’ focus on quality and improving the safety of underground workers, is a very fitting host for DRS,” said Gisle Østereng, CEO of Dynamic Rock Support AS “With the backing of Normet’s worldwide organization, the technology and expertise fostered by DRS will continue to impact mining and tunneling operators with world-class ground support and rock reinforcement products.”