Open pit mining in Western Australia

Challenges and lessons learnt - Rock has a voice and indeed it has memory

Phil Dight

After 50 years in the practice of geotechnical engineering in the mining industry and trying to implement what I have learnt along the way, the plan is to try and couple together some of the findings which are often not explained or covered in geotechnical teaching and some challenges ahead. I can say I am still learning.

The answer for what is happening is so often in the geology which can be a struggle for me as an engineer. However, much can be learnt from operators and colleagues with diverse training. Some of the findings I have learnt in Western Australia will be presented, including ground support, groundwater, toppling, rotational failure, planar failure, how to read the information in a stereonet and what more I can learn, clarifying the difference between faults and shears from a geotechnical perspective, monitoring, limitations of limit equilibrium analysis, and an answer to a question raised in the Large Open Pit Guidelines for Open Pit Design on whether the stress changes are important in the design of slopes of an open pit mine.

About the speaker

Phil Dight Professor of Geotechnical Engineering Australian Centre for Geomechanics The University of Western Australia

Phil has been involved with the development and design of ground support for mining applications since 1975. He was a partner in BFP Consultants until BFP was acquired by Coffey Mining. Phil has extensive consulting experience in the geotechnical aspects of the mining industry, and has worked on open pit and underground metalliferous mining problems. In 1985 he was awarded the Manuel Rocha Medal by the International Society of Rock Mechanics (ISRM) for his work in open pit mining and use of ground support to improve pit stability. His ground support algorithm has been adopted by Rocscience in its evaluation of ground support in Phases® and Itasca in 3DEC®. Rocscience also adopted his algorithm for RocTopple®. With Peter Fuller, he undertook research into ground support work in several AMIRA sponsored underground projects. Much of that early research work was formalised in the literature by others. Phil joined the ACG in 2008 and has since been working on in situ stress determination, ground support applications (eg BoltCalc®, fibrecrete), strainburst and slope stability problems. At UWA he has developed a research laboratory looking at rock properties in 3D. He is active in training site personnel in geotechnical engineering based on practical applications and on request, he continues to provide specialist consulting.

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