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Validation of entry stability factors determined by the strength reduction method against empirical approaches.

Authors
Esterhuizen-GS; Bajpayee-TS; Murphy-MM; Ellenberger-JL
Source
Proceedings of the 32nd International Conference on Ground Control in Mining, July 30-August 1, 2013, Morgantown, West Virginia. Morgantown, WV: West Virginia University, 2013 Jul; :82-89
NIOSHTIC No.
20043218
Abstract
The design of support for underground excavations is a complex process in which the interaction between supports and the rock mass must be evaluated. The strength reduction method (SRM) is useful because it provides a stability factor of the supported excavation that can easily be compared between support alternatives. The method is based on numerical model analysis where the stability factor is determined by reducing the rock mass strength until collapse is indicated in the model. This paper presents the results of validation studies that were conducted using the FLAC3D stress analysis software to compare SRMcalculated stability factors to the empirically based Coal Mine Roof Rating (CMRR) and the Analysis of Roof Bolt Systems (ARBS). The objective was to determine whether the SRM, with its basis in mechanics, would predict similar outcomes as the fundamentally different ARBS and CMRR methods with their basis in empirical observations. A total of 450 different scenarios were evaluated in which the geology, horizontal stress, depth of cover, entry width, support spacing, and support length were varied. The results showed that the SRM-calculated stability factors were able to satisfactorily capture both the "weak bed" and "strong bed" adjustments in the CMRR. The SRM results were found to be well correlated to the ARBS stability factors for the 450 cases considered. Further analysis showed that the SRM accurately captures the effect of bolt length, depth of cover, and entry width on the overall stability of an entry.
Keywords
Mining-industry; Underground-mining; Ground-control; Ground-stability; Geology; Stone-mines; Computer-software; Computer-models; Models
Publication Date
20130730
Document Type
Conference/Symposia Proceedings
Fiscal Year
2013
NTIS Accession No.
NTIS Price
NIOSH Division
OMSHR
Priority Area
Mining
Source Name
Proceedings of the 32nd International Conference on Ground Control in Mining, July 30-August 1, 2013, Morgantown, West Virginia
State
PA; WV
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