When excavating an underground tunnel, mining crews must reinforce newly exposed rock using long anchor bolts, known as rock bolts, to stabilize the external walls by transferring the load to the interior of the rock mass. The installation of this rock support is carried out as an integral part of providing safe ground control in underground excavation.
Through a collective effort involving engineers, operators and maintenance crews, Newmont’s Leeville team has again risen to the challeng of improving site safety and productivity.
A new rock bolt was conceived by Leeville employees that improves bolt installation and resistance to ground movements. This new bolt, dubbed the “Nevada” bolt, is a yielding bolt: a hollow steel threaded bar that self-drills or is inserted into a predrilled hole. Grout is then pumped through the center of the bolt and back out around the bolt to secure it in the hole.
A challenge still remained regarding bolt installation. The process required the bolts to be installed with bolting machines and temporarily held in place until crews could manually hook up the grouting equipment. Because manual access was required, the support had to be installed after primary support was installed, causing delays and additional expense. In addition, while resin and pumping technologies are available on the market, no device was available to “connect or couple” the resin system through the bolt itself, from the bolter, to perform the grouting.
Despite the many challenges, the Leeville team came up with a robust and efficient solution – designing an innovative resin head insert that would be sealed through the simple act of pushing the head on the bolt by the feed action of the drill.
Engineers, operators, and maintenance teams worked together to develop this “ShoGun” head. After a few successive prototypes were trialed, the system was deemed functional as the targeted time for bolt installation was achieved.
The Leeville team undertook the task of automating the process so the “Nevada” hollow core bolts could be installed in a first pass process, thereby eliminating the need for manual access and temporary support. This greatly improves safety while reducing costs.
Congratulations to Newmont’s Leeville mine team for their innovations and commitment to safety and productivity improvements.