The 'Guidelines for Open Pit Slope Design' developed as part of the Large Open Pit (LOP) project was published in 2009. The guidelines were focused on hard rocks in open pit mines so did not address design issues for pit slopes in materials generally classed as weak rocks. Research currently being undertaken by the LOP sponsors is directed at filling this gap.Canvassing of the LOP sponsors and their affiliates resulted in identifying pit slope issues in five general categories of weak rocks:1. Cemented transported sediments.2. Saprolites (residual soils and weathered rocks).3. Leached rocks/soft iron ores (leached, creating a rock with a high void ratio).4. Mudrocks.5. Hydrothermally altered rocks.Establishing the strength of hard rocks is traditionally approached using rock mass classifications and the Hoek-Brown failure criterion. However, there is ample evidence that these approaches do not capture the strength characteristics and the failure processes evident in weak rocks. In this paper the authors describe some of the processes that should be considered when attempting to establish the strength and failure envelopes input into slope designs for open pits in weak rocks.
展开▼
