Tag Archives: rock bolts

Montana Tech puts Epiroc Swellex bolts to the test

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Mining engineering students at Montana Technological University are testing bolt integrity when loaded using a Ground Support Pull Test Kit and Swellex bolts donated by Epiroc.

The Montana Tech mining engineering program provides students with education, access to cutting-edge labs and participation in leading research, Epiroc says. The school has the only on-campus underground mine education centre in the US and uses it to give students hands-on experience.

“Working with modern equipment is also an important part of preparing students for the workforce,” Epiroc says. For this, the Mining Engineering department often relies on donations from equipment manufacturers.

Students are testing how much load and deformation they can get from Swellex bolts without losing integrity. This test project began as a challenge from a leading mining corporation.

To help make the project a reality, Epiroc donated the Ground Support Pull Test Kit and Swellex bolts, with an Epiroc team led by Adrian Berghorst, Segment Business Manager – Ground Support, and Eric Ball, Northwest District Sales Manager – Rock Drilling Tools, providing installation and hands-on training support.

As part of the test, sleeves will be used on bolts to qualify the critical bond length of Swellex bolts under forced displacement without loss of integrity in the bolts. The Pull Test Kit supplied will be essential to testing the bolts’ load and deformation characteristics in that rock mass and borehole.

In addition to benefiting the students, the research performed also allows the school to publish their findings, Epiroc says.

Scott Rosenthal, Mining Engineering Department Head, Associate Professor, Mining Engineering at Montana Tech, said: “With access to this equipment, students can do something unique and different. We thrive thanks to the support of industry partners like Epiroc.”

Shawn Cheney, Epiroc Business Line Manager – Rock Drilling Tools, added: “Partnering with Montana Tech helps give the next generation of miners a great start, enables additional research on mining limitations and capabilities, and gives Epiroc additional insights so we can continue our ongoing quest for improvement in mining.”

Mining3 to expand rock bolt safety testing for underground mines

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Mining3 Technology Leader, Sam Spearing, says developing more effective rock bolt designs that not only take tension into consideration but also bending and shear (guillotine) could significantly improve safety.

In addition, the basic rock bolt could serve a greater purpose by showing principal stress directions in the immediate rock, which could be used to better calibrate computer simulations, according to Spearing.

“Rock bolts have formed part of the underground mining environment since the 1890s and are effective in stabilising and controlling the immediate roof and ribs (sides) of tunnels.

“Although they are an integral part of the underground mining support structure, very little is known about the actual load distribution along a rock bolt. Current design practice only considers the axial load capacity of the rock bolt yet they are subjected to combinations of axial, shear and bending, in situ.”

Rock bolts are generally exposed to a combination of shear, bending and tension that can cause the bolt to deform with increasing displacements along and across faults, joints and beds, potentially leading to failure, Spearing said. In spite of these combined effects, only tensile capacity is currently considered in design and testing.

Adding to this design oversight, tensile capacity isn’t the weakest performance link. Shear capacity, on the other hand, holds roughly 70% of tensile strength, which leads to support designs that tend to overestimate the rock bolts effectiveness, according to Spearing.

Mining3 is currently working on a project to:

  • Understand in-situ rock bolt performance;
  • Develop computer models that provide a more accurate and visual representation of how rock bolts perform underground;
  • Determine the principal stress directions close to excavations, and;
  • Create instrumented rock bolts that can measure load along the length.

Spearing said: “A broader outcome of this project will be the ability to remotely monitor the loading on rock bolts in real time from a control centre on the surface. Providing this level of visibility would allow miners to better predict failures and avoid them, which could be a game changer in the field of rock related safety in underground mines.”

A separate follow-up project is already approved and funded to design a specific instrument to measure total strain in the immediate roof or rib, according to Spearing.

Current technology being tested in conveyor monitoring has a similar application in which, through the use of fibre optics, it is able to pick up signature acoustics that indicate movement related to stages of failure in rollers, according to Spearing. “In the case of monitoring rock bolts, if fibre optic cable is adhered on or within the rock bolt, it will enable the detection of ground movement. Data is analysed, interpreted and presented from an offsite control centre and could indicate where and when tunnel failure may occur,” he said.