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Mining Publication: A Case Study of Bolt Performance in a Two-entry Gate Road
Keywords: Cable bolts Field measurement Mechanical strain Resin bolts Support design and selection
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 1998
Authors: SP Signer, JL Lewis
Conference Paper - August 1998
Download PDF Document (0.79 MB)
17th Conference on Ground Control in Mining, West Virginia University, August, 1998; :249-256
This paper presents the results of a case study conducted in a two-entry gateroad in a coal mine where excessive roof deformation and bolt loading resulted in failure of many roof supports. The instruments consisted of 16 fully grouted, strain-gaged resin bolts, load cells on both full and partially grouted cable bolts, and vertical deflection multipoint extensometers. These instruments were installed on-cycle to measure loading on bolts in an existing support pattern and to determine if cable bolts could be used to improve roof stability. Results showed significant amounts of movement within the bolted zone. In some cases, these movements were enough to load the supports past their ultimate strength. Geology appeared to be a significant factor in localized roof degradation; that is, a very weak rock layer in the immediate roof overlain by a very strong rock layer contributed to the development of shear planes. Only one instrumented bolt had a maximum strain of less than 2,000 microstrain, which was the yield point of the steel. The average maximum strain on all bolts was 20,000 microstrain. However, electrical continuity to many gages was lost, and a pattern was noted that would indicate possible bolt failure. Wire mesh and concrete cans installed as secondary support performed very effectively.
Image of publication A Case Study of Bolt Performance in a Two-entry Gate RoadConference Paper - August 1998
Download PDF Document (0.79 MB)
17th Conference on Ground Control in Mining, West Virginia University, August, 1998; :249-256
See Also
Determination of Physical Properties of Cable Bolts in Cement Grout Pull Tests Using Instrumented King Wires
Diagnosing and Controlling Moisture-Sensitive Roof in Coal Mines
Ground Support Factor of Safety Calculator - 1.1.11
Optimizing Secondary Roof Support with the NIOSH Support Technology Optimization Program (STOP)
Overview of Coal Mine Ground Control Issues in the Illinois Basin
Pillar and Roof Span Design Guidelines for Underground Stone Mines
Technology News 476 - Instrumented King Wire for Monitoring Cable Bolts
Technology News 482 - Ground Support Safety Training Video
Tests of Fibre-Reinforced Shotcrete at the Chief Joseph Mine, Butte, Montana
Updating the NIOSH Support Technology Optimization Program (STOP) With New Support Technologies and Additional Design Features
Page last reviewed: September 21, 2012
Page last updated: September 21, 2012
Content source: National Institute for Occupational Safety and Health, Mining Program
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