Ground Fall Mitigation Capability and Enhanced Testing for Rockburst Susceptibility of Rock Liners
| Principal investigator(s): | James Archibald
(Queen's University) |
| Co-investigator(s): | P.D. Katsabanis
(Queen's University) |
| Sponsoring Institution: | Queen's University |
Objective
Because future mining development in this province is expected to take place at greater depths than presently mined, the incidence of rock falls and rockbursts, and thus worker injuries, is projected to increase. The objective of this study was to build on previous RAC-funded research to assess further the capabilities of conventional forms of mine reinforcement media and new thin, spray-on linings (TSL’s) to provide effective structural support for rock excavations in underground mines.
Method
A systematic process of material characterization that had been developed in earlier research was rigorously carried out to permit side-by-side comparison of TSL characteristics for seven new products and eleven TSL products in total. Blasting trials were conducted upon exposed rock in a surface site where damage effects were monitored using high-speed digital and other photographic analytical techniques. Ground vibration conditions (notably particle velocity characteristics of ground motion) were also monitored at each detonation site using multiple sensors to insure that systematic and repeatable test conditions were maintained for all support materials. Each test site occupied a zone of outcrop sized at 4 metres by 5 metres in plan. Measured ground displacement, velocity, and acceleration characteristics resulting from each blast provided information to permit comparison of support effectiveness between sites. Post-blast damage assessment was also conducted through systematic analyses of digital blast images, ground motion data, extent of fracture zone created, and conditions of support media damage. Ground motion and outcrop fracture incidence were uniformly maintained between successive tests by rigorous adherence to fixed explosives loading geometry conditions.
Results
The results obtained from this research effort have validated the assumption that this new and innovative support technique may be equivalent to or substantially better than conventional support methods in providing safe, capable and sustainable support in the event of dynamic rock failure. The entire range of TSL types evaluated has demonstrated an ability to deform substantially and to therefore constrain fragment or loose rock ejection created by energetic and natural rock breakage. By so doing, these tenaciously-adhering, deformable cover materials have also demonstrated an ability to substantially mitigate damage often seen to result when catastrophic unsupported rock failure occurs.
Conclusions
The wide-ranging series of tests completed have verified that spray-on forms of area support, including conventional concrete materials such as shotcrete and fibrecrete linings, innovative TSL’s, and combinations of both forms of sprayable support agents (designated as "Superliners") all demonstrate significant and positive support benefit and abilities to resist rockburst-induced damage relative to conventional support media. Significant worker hazards are known to currently exist in Ontario mines where use of conventional support measures is the norm. Implementation of new support technologies may therefore realize reduction of worker hazards in current operating mines and help to prevent escalation of hazards when future deep mining occurs. The relative merits of a variety of forms of spray-on lining support materials (conventional and TSL types) for mitigating rockburst damage have been effectively demonstrated through the course of this research effort. Many of the spray-on products appear to be viable for rock support use, and should therefore be contemplated for systematic underground application trials by industry.
The results of laboratory tests have identified several promising TSL agent materials that may be potentially very effective in mitigating rockburst damage to both the support materials and rock surfaces onto which the materials were placed. TSL support technology appears to be viable for reducing rockburst hazards associated with rock fracturing, fragment ejection and loss of support capacity, as was noted to occur for conventional rock support media. For these benefits alone, the application of TSL support technologies would be very beneficial for reducing worker hazards in underground rockburst-prone environments. Safety benefits have been shown where TSL media have been tested under highly dynamic failure conditions. It would also be anticipated that such support measures would realize significant support restraint in lower stress environments, where worker injury from falls of loose ground are also common.
Publications
Archibald J. F., Dirige A.P., Katsabanis P.T. (2005). "Evaluation of New and Combined Area Support Systems for Rockburst Damage Mitigation." Presentation at the 20th Symposium on Ground Control: The Impact of Ground Control on the Success of Mining Operations, Quebec Mining Association, Val d’Or, Quebec, March 22-24, 2005. CD-ROM publication (21 pages).
Archibald J. F., Dirige A.P., Katsabanis P.T. (2005). "Update on WSIB Research Into Testing of New Spray-On Liner and Composite ‘Superliner’ Area Supports." Presentation at the Mining Health and Safety Conference 2005, Mines and Aggregates Health and Safety Association of Ontario, Sudbury, Ontario, April 12-14, 2005. CD-ROM publication (23 pages).
Archibald J.F., Dirige A.P. (2005). "Spray-On Lining Innovation for Support in Burst-Prone Mine Environments and Tunnel Coatings in Civil Engineering Use." Presentation at the 40th U. S. Rock Mechanics Symposium, Fairbanks, Alaska, June 2005.
Dirige A.P., Archibald J.F. (2005). "Simulation of Pull-Tests for Thin Spray-on Liners." Presentation at the 40th U. S. Rock Mechanics Symposium, Fairbanks, Alaska, June 2005.
Archibald J.F., Dirige A.P. (2005). "Use of Spray-On Linings for Effective Structural Support in Civil and Mining Applications." Presentation at the K. Y. Lo Symposium, University of Western Ontario, July 2005.
Archibald J.F., Dirige A.P. (2006). "Safety Considerations Associated with Thin., Spray-On Liners Used for Mining and Civil Engineering Applications." Presentation at MASHA Mining Health and Safety Conference, Sudbury, Ontario, April 2006.
Archibald J.F., Dirige A.P. (2006). "Development Status of Thin, Spray-On Liners for Mining and Civil Engineering Applications." Presentation at the Annual General Meeting of the Canadian Institute of Mining, Metallurgy and Petroleum, Vancouver, British Columbia, May 13-17, 2006.
Archibald J.F., Dirige P.A. (2006). "Thin, Spray-On Lining Applications for Rockburst, Blast and Fire Damage Mitigation." Presentation at the 41st Symposium of the United States Rock Mechanics Society (ARMA/USRMS 06-1005), Golden, Colorado, June 17-21, 2006.
Archibald J.F., Dirige P.A. (2006). "Development of Thin, Spray-On Liner and Composite Superliner Area Supports for Damage Mitigation in Blast-and Rockburst-Induced Rock Failure Events." Presentation at the 9th International Conference on Structures Under Shock and Impact (SUSI 2006), Liverpool, UK, July 1-6, 2006.
For more information:
archibal@mine.queensu.ca
| | |
