ABSTRACT:

The main goal of this study is to evaluate how the mining of the West Ore body (WOB2 and WOB3) affects the stress conditions in the crown pillars as mining progress upwards. Also, this analysis determines the “transition zone” in crown pillar at which significant changes are likely to occur, and when changes to the mining method and ground support are required. The intent is to determine the minimum crown pillar thickness that could be mined with current post pillar cut-and-fill method. The West Ore body is divided into two mining zones, WOB2 and WOB3 with the current back elevations of 9095 (cut 7) and 8702 (cut 4), respectively. This study includes two and three dimensional numerical models .A finite element program “Phase2” was used to plastically estimate the displacement and stress at the core of crown pillars. The Bob’s Lake Fault and backfill were incorporated into the model. The 3D boundary element program “MAP3D” was used to obtain the elastic stress and displacement at different locations and elevations. Also, the 3D analyses were used to evaluate the effects of mining in Main Ore body on the West Ore body. The two and three dimensional numerical analysis results along with field observation and historical microseismic data suggest that; 1) Due to the narrow nature and dip of the ore body in WOB2, the cut -and-fill mining may need to be converted to bulk mining from Cut 10/Cut 11 and above. 2) As mining advances upwards in WOB3, the very high deviatoric stresses zone would form in the back at Cut 15. In WOB3, the crown pillar thickness should be limited to a minimum of 90 ft.

1. INTRODUCTION

Coleman Mine is located about 50 km north-west of Sudbury, within the limits of the City of Greater Sudbury.

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