Risk management and remediation of the north wall slip, West Angelas Mine, Western Australia

Abstract

A planar failure of approximately 600 kT occurred on the north wall of Centre Pit North (CEPN) at West Angelas Mine site in February 2010. The failure impacted a substantial resource of high grade iron ore and left a number of significant geotechnical hazards on and adjacent to the failure surface. These presented a series of challenges which had to be overcome in order to remediate the failure and reclaim the bulk of the buried ore. A number of recovery options were investigated and presented to management. This paper outlines the plan which was adopted, the challenges encountered during its implementation and the risk management and mining procedures used to bring the remediation and recovery to a successful conclusion. A significant fall of ground occurred on the north wall of CEPN at the West Angelas Mine site on the evening of the 3 February 2010. The failure occurred in the Mount Newman Member of the Marra Mamba Iron Formation, which is comprised predominantly of banded iron formation (BIF) with interbedded shale. Bedding dip was roughly parallel to the overall slope angle, except where it flattened towards the pit, on the lower benches. The failure was due to planar sliding on the NS2 shale, which was daylighted in places, towards the toe of the slope. The resultant failure surface is approximately 112 m high, dipping at an average of 42°. The failed rill heap of approximately 600 kT, covered a significant resource of high grade iron ore.

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“…This enables automated acquisition of data and also links to the Geoscience Monitoring Data System (GMDS). TDRs were installed as part of the remediation plan of a significant instability at one of the Pilbara operations (Joass et al, 2013).…”