Location
New York, New York
Date
16 Apr 2004, 8:00am - 9:30am
Abstract
Area 1 of Doe Run Company’s Buick North Mine was selected for placement of cemented rockfill (CRF) to “trap” or encapsulate select pillars. This method of “trapping” pillars takes advantage of the passive confinement effect of CRF to increase the post-peak load bearing ability of trapped pillars so that other ore bearing pillars can be extracted while still maintaining local and global mine stability. A total of 73 pillars in this area were extracted from October 1998 thru January 2002. Thirteen of 73 pillars were totally trapped by CRF (i.e., the pillars were totally encased in CRF). Eight of the thirteen pillars trapped with CRF were instrumented with extensometers to monitor deformations that occurred during the extraction process. Of the remaining pillars, 18 were not confined in CRF; and the remaining pillars were partially trapped to some degree (one or more free faces). Data collected from the instruments showed that the rate at which pillars deformed (or converged) slowed and that most of the instrumented pillars were virtually unaffected until the late stages of pillar extraction. Two of the instrumented pillars showed considerable initial vertical strain at the onset of pillar extraction. The rate at which these pillars converged slowed as additionally pillars were extracted. This was attributed to the passive confinement effect of CRF in which this material compacts (the density increases) as the pillar dilates, becomes stiffer, and thus provides an increase in confining pressures or stress that acts to restrict pillar dilation. This study has provided valuable insight into the behavior of trapped roof supporting pillars during the extraction process. Future research is being undertaken to clearly develop procedures to predict the behavior CRF trapped pillars during extraction of other economically valuable pillars.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
5th Conference of the International Conference on Case Histories in Geotechnical Engineering
Publisher
University of Missouri--Rolla
Document Version
Final Version
Rights
© 2004 University of Missouri--Rolla, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Zur, Kenneth J. and Apel, Derek, "Use of Cemented Rock Fill for Enhanced Pillar Recovery in Area 1 of the Doe Run Company" (2004). International Conference on Case Histories in Geotechnical Engineering. 26.
https://scholarsmine.mst.edu/icchge/5icchge/session06/26
Use of Cemented Rock Fill for Enhanced Pillar Recovery in Area 1 of the Doe Run Company
New York, New York
Area 1 of Doe Run Company’s Buick North Mine was selected for placement of cemented rockfill (CRF) to “trap” or encapsulate select pillars. This method of “trapping” pillars takes advantage of the passive confinement effect of CRF to increase the post-peak load bearing ability of trapped pillars so that other ore bearing pillars can be extracted while still maintaining local and global mine stability. A total of 73 pillars in this area were extracted from October 1998 thru January 2002. Thirteen of 73 pillars were totally trapped by CRF (i.e., the pillars were totally encased in CRF). Eight of the thirteen pillars trapped with CRF were instrumented with extensometers to monitor deformations that occurred during the extraction process. Of the remaining pillars, 18 were not confined in CRF; and the remaining pillars were partially trapped to some degree (one or more free faces). Data collected from the instruments showed that the rate at which pillars deformed (or converged) slowed and that most of the instrumented pillars were virtually unaffected until the late stages of pillar extraction. Two of the instrumented pillars showed considerable initial vertical strain at the onset of pillar extraction. The rate at which these pillars converged slowed as additionally pillars were extracted. This was attributed to the passive confinement effect of CRF in which this material compacts (the density increases) as the pillar dilates, becomes stiffer, and thus provides an increase in confining pressures or stress that acts to restrict pillar dilation. This study has provided valuable insight into the behavior of trapped roof supporting pillars during the extraction process. Future research is being undertaken to clearly develop procedures to predict the behavior CRF trapped pillars during extraction of other economically valuable pillars.
