Geotechnical Design Methods at Smoky River Coal Limited

ABSTRACT

Smoky River Coal Limited opened a new underground operation, the 5B-4 Mine, in January, 1998. The mining plan proposed the use of retreat room and pillar mining methods at depths of up to 550 m (1800 ft.), well beyond conventional limits, beneath a roof that was predicted to be severely affected by shearing, thrust faulting, slickensiding and abrupt changes in dip.

Under such circumstances, the problems associated with pillar design and roof support were addressed by the inclusion of a geotechnical program in the operations plan. The geotechnical program included a review of design methods, monitoring of pillar and roof behaviour and training of operations personnel.

The program resulted in:

improved pillar design methodologies, reflecting themost up to date understanding of pillar performance, leading to the adoption of stable narrow pillar designs that assisted in improving mining efficiency

improved roof support design methods, allowing for a change to operator-lead decisions on optimum roof bolt support under the various roof types encountered, and

technological improvements in bolting hardware and drilling technology that assisted in the completion of operations tasks and in improved safety conditions.

This paper summarizes the work accomplished on each ofthese topics prior to the closure of the mine, whichoccurred in March of 2000 as a result of low coal pricesand a large corporate debt load.