Rock Mass Response to Mining Activities: Inferring Large-Scale Rock Mass Failure

Mining activities may result in rock mass deterioration and instability that may lead to failure both in underground and open pit mines. Such deterioration represents a safety risk and may result in substantial financial losses. Rock mass response may lead to ground subsidence, fall of ground/caving, inundation, pillar collapse, seismic activities and slope and tailings dam instability. Each response is preceded by warning signs and precursors, which are identified in this book, with a view to providing guidelines for prediction and amelioration of damage to mining structures. Furthermore, case studies of both large scale ground deterioration leading to collapse and geotechnical mine disasters are presented. Identifying risks and monitoring geotechnical precursors and warning signs allows for safe and productive mining.

Author Biography: Dr Tadeusz Szwedzicki is an internationally recognised expert in geomechanics of underground mining methods. He has over 40 years of mining experience working in mining production, research and development, and consulting. His experience has been gained working for some of the world's largest mining companies like PT Freeport (Indonesia), ZCCM (Zambia), Anglo American Corp (Republic of South Africa), and WMC and BHP Billiton (Australia). He had academic positions at Western Australian School of Mines, and University of Zimbabwe. His experience also includes government positions at the Northern Territory department of Mines and Energy where he was appointed the Government Mining Engineer and the Government of Papua New Guinea as Mineral Resources Advisor. He is a recipient of the Silver Medal awarded by the Institution of Mining and Metallurgy, London, and a recipient of Fulbright scholarship, USA. He has authored over 70 papers including in the International Journal of Rock Mechanics, Transactions of the Institute of Mining and Metallurgy, and proceedings of international conferences. He is an independent consultant specializing in geomechanics of mining methods.

1 Introduction 2 Factors affecting rock mass response to mining 2.1 Geotechnical factors affecting rock mass response 2.2 Mining factors affecting rock mass response 2.3 Effect of mining scale on response of rock mass 3 Case studies of rock mass response to underground mining 3.1 Case studies of surface crown pillar collapse 3.2 Case studies of rockbursts and outbursts 3.3 Case studies of uncontrolled caving and pillar collapses 3.4 Case studies of damage to underground mining infrastructure 4 Case studies of rock mass response to surface mining 4.1 Open pit slope failure due to underground mining 4.2 Slope failure along geotechnical structures 4.3 Collapse of a highwall in an open pit 5 Case studies of inundations 5.1 Water inrush into a colliery 5.2 Tailings inrush into an underground mine 5.3 Backfill liquefaction and inrush into a mine 5.4 Mud inrush resulting from collapse of a crown pillar 5.5 Instability of waste rock tip 5.6 Instability of tailings dam 5.7 Progressive failure of coal refuse dam 5.8 Failure of tailings dams triggered by earthquakes 6 Effect of discontinuities on the initiation of failure process 6.1 Modes of failure of rock samples 6.2 Effect of discontinuities on strength of rock samples 7 Behaviour of rock mass prior to failure 7.1 Pre-failure warning signs 7.2 Sequence of precursors to rock mass failure 7.3 Geotechnical risk management 7.4 Monitoring of precursory behaviour 8 Rock mass behaviour during failure 8.1 Case studies on onset of failure 8.2 Case studies on duration of failure 8.3 Progressive damage to excavations under high mininginduced stress 9 Post-failure rock mass behaviour 9.1 Case studies of post-failure behaviour 9.2 The effect of mining geometry on post-failure behaviour 10 Modes of failure of rock and rock mass 10.1 Modes of failure at a sample scale 10.2 Mode of failure at a local scale 10.3 Mode of failure at a mine scale 11 Behaviour of fragmented ore 11.1 Ore flow - a case study from a block caving mine 11.2 Behaviour of fragmented ore - a case study from a sublevel caving mine 11.3 Analysis of a diameter of a draw zone from two case studies of caving mines 11.4 Behaviour of fragmented ore in orepasses 12 Mitigation of rock mass response through geotechnical quality assurance 12.1 Quality in ground control 12.2 Quality assessment 12.3 Quality assurance in ground control management system 12.4 Quality assurance in geotechnical planning and design 12.5 Quality assurance in ground control activities 12.6 Quality assurance in geotechnical inspection and monitoring