A design philosophy for surface crown pillars of hard rock mines

CIM Bulletin, Vol. 80, No. 903, 1987

MARC C. BETOURNAY, Rock Mechanics Laboratory, CANMET-EMR, Ottawa, Ontario

Surface crown pillars, acting to safely protect underground workers and operations from surface elements, are recognized, herein, as distinct from conventional deeper underground pillars. Moreover, because of the variation in mining and geological conditions that exist from mine site to mine site, each case is viewed as unique. A review of numerous case studies and existing literature indicates that there is little general information or systematic problem-solving approach associated with them. A design process, not unlike that of other engineering disciplines, is presented to correct these deficiencies. As part of its purpose, it will inform operators of the key elements required for design and will address the problems of these appendages. The design, while taking into consideration possible surface crown pillar settings and inherent characteristics, is founded on a step-by-step procedure starting with site investigations through to monitoring or pillar recovery. The process is flexible, in that it incorporates decision making and changes in mining strategy. The purpose of each step is explained and each step is extensively described in terms of the required equipment and methods for field work, analysis and support measures. Analytical formulae and studies from several fields directly applicable to surface crown pillars are also given. Recommendations for future research studies are presented.

Mots Clés: Rock mechanics, Surface crown pillars, Canadian mines, Design philosophy, Design process, Geotechnical investigations, Mining strategy, Design methods, Mining activity, Monitoring, Back analysis, Pillar recovery, Design evaluation.