Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content

Mining Publication: Field Test with Strain-Gauged Friction Bolts at the Gold Hunter Mine, Mullan, Idaho, USA

NOTE: This page is archived for historical purposes and is no longer being maintained or updated. Contact NIOSH Mining if you need an accessible version.

Original creation date: August 2003

Image of publication Field Test with Strain-Gauged Friction Bolts at the Gold Hunter Mine, Mullan, Idaho, USA

To measure the loading behavior of friction bolts, NIOSH researchers installed strain gauges on the interior of friction bolts and developed a battery-powered miniature data acquisition system (MIDAS) that fits inside the hollow portion of the friction bolt. The advantages of this system are that it is protected from face blasts and eliminates the need for external wiring. Laboratory pull-out tests showed that friction bolts installed in a concrete block with resin were loaded to about 1.8 tons/ft of bolt length; bolts installed without resin were loaded to 1.3 tons/ft. Three strain-gauged friction bolts were installed at Hecla Mining Company's Gold Hunter Mine, Mullan, ID, in the wall or rib of a mechanized cut-and-fill stope. The object of these tests was to establish an installation procedure for the bolt-and-MIDAS combination and to evaluate performance. The stope was advanced in three 15-ft increments and strains induced in the rock bolts by stress changes in the rock were recorded every 30 minutes. The MIDAS proved to be rugged enough to withstand the shock and vibration from nearby (5 ft) face blasting. Data from MIDAS showed that the friction bolt installed with resin was the most sensitive to each face advance. It showed a steady increase in loading to a maximum value of 1000 microstrain. The friction bolt installed without resin showed stick-slip behavior with loads to a maximum of 400 microstrain before the stope was completed.

Authors: JC Johnson, TJ Williams, CB Sunderman, SP Signer, DC Bayer

Conference Paper - August 2003

NIOSHTIC2 Number: 20030805

In: S. S. Peng, C. Mark, A. Wahab Khair, and K. Heasley, eds., Proceedings: 22nd International Conference on Ground Control in Mining (Aug. 5-7, 2003; Morgantown WV), Dept. of Mining Engineering, West Virginia University, 2003 Aug; :233-239